introductory engineering graphicsdl.booktolearn.com/ebooks2/computer/graphics/... · 2019-06-23 ·...

INTRODUCTORYENGINEERINGGRAPHICS

INTRODUCTORYENGINEERINGGRAPHICS

EDWARDE.OSAKUE

IntroductoryEngineeringGraphics

Copyright©MomentumPress®,LLC,2018.

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, ortransmitted in any formor by anymeans—electronic,mechanical, photocopy, recording, or any other—exceptforbriefquotations,nottoexceed400words,withoutthepriorpermissionofthepublisher.

FirstpublishedbyMomentumPress®,LLC222East46thStreet,NewYork,NY10017www.momentumpress.net

ISBN-13:978-1-94708-360-8(print)ISBN-13:978-1-94708-361-5(e-book)

MomentumPressGeneralEngineeringandK-12EngineeringEducationCollection

CoverandinteriordesignbyExeterPremediaServicesPrivateLtd.,Chennai,India

10987654321

PrintedintheUnitedStatesofAmerica

http://www.momentumpress.net

ABSTRACT

Introductory Engineering Graphics concentrates on the main concepts andprinciples of technical graphics and provides users with the information theyneedmost in aneasyand straightforwardmanner.Thechapters and topics areorganizedinasequencethatmakeslearningagradualtransitionfromonelevelto another.However, eachchapter ispresented in a self-containedmanner andmay be studied separately. In each chapter, techniques are presented forimplementingthetopicstreated.Chapter1discussestheguidelinesfordrafting.Chapter2presentstheprinciplesandtechniquesforcreatingstandardmultiviewdrawings. Chapter 3 discusses auxiliary view creation, whereas Chapter 4focuseson sectionviewcreation.Basicdimensioning is covered inChapter5.IsometricpictorialsarepresentedinChapter6.WorkingdrawingsarecoveredinChapter 7, the heart of drafting, and practical information is provided forcreating them. The Appendices provide introductory discussions about screwfasteners,generalandgeometrictolerancing,andsurfacequalityandsymbols.

Thisbookisdesignedasamaterialforinstructionandstudyforstudentsandinstructors of engineering, engineering technology, and design technology. Itshould be useful to technical consultants, design project managers, computerdesign drafting (CDD) managers, design supervisors, design engineers, andeveryoneinterestedinlearningthefundamentalsofdesigndrafting.Thebookiswritten with full cognizance of current standards of American NationalStandardsInstitute/AmericanSocietyforMechanicalEngineers(ANSI/ASME).Thestyleisplain,anddiscussionsarestraighttothepoint.Itsprincipalgoalismeetingtheneedsoffirst-andsecond-yearstudentsinengineering,engineeringtechnology,designtechnology,andrelateddisciplines.

KEYWORDS

auxiliary views, CDD, design, dimensioning, graphics, isometric views,

multiviewdrawings,orthographicprojection,sectionviews,shapeconstruction,technical,workingdrawings

11.11.21.31.41.51.61.71.81.91.101.11

22.12.22.32.42.52.62.7

CONTENTS

LISTOFFIGURES

LISTOFTABLES

PREFACE

GUIDELINESFORDRAFTING

IntroductionConventionsandStandardsDrawingUnitsDrawingMediaSheetLayoutAnnotationsLinestylesPrecedenceofLinestylesApplyingLinestylesChapterReviewQuestionsChapterExercises

STANDARDORTHOGRAPHICDRAWINGVIEWS

IntroductionProjectionTypesOrthographicProjectionConceptsandAssumptionsObjectPlanesandFeaturesBoundingBoxConceptVisualizinganOrthographicViewProjectionDrawingViews

2.82.92.102.112.122.132.14

33.13.23.33.43.53.63.73.8

44.14.24.34.44.54.64.74.84.94.104.11

55.15.2

NonuniqueViewsRequiredViewsandPlacementConstructingStandardMultiviewsGeneratingViewsfromSolidModelsChecklistforMultiviewDrawingsChapterReviewQuestionsChapterExercises

AUXILIARYDRAWINGVIEWS

IntroductionUnderstandingAuxiliaryViewsVisualizingAuxiliaryViewsConstructingAuxiliaryViewsGeneratingAuxiliaryViewsfromSolidModelsCombinedStandardandPartialAuxiliaryViewsChapterReviewQuestionsChapterExercises

SECTIONDRAWINGVIEWS

IntroductionConceptofSectionsCuttingPlaneLineStylesHatchPatternsSectionViewRepresentationandPlacementSectionViewTypesConventionalBreaksConstructingSectionViewsGeneratingSectionViewsfromSolidsChapterReviewQuestionsChapterExercises

BASICDIMENSIONING

IntroductionEngineeringDrawingandSizeDescriptions

5.35.45.55.65.75.85.95.105.11

66.16.26.36.46.56.66.76.86.96.10

77.17.27.37.47.57.67.77.87.97.10

DimensionElementsandSymbolsDimensionTypesandLineSpacingPlacingDimensionsonObjectFeaturesDimensioningMethodsDimensionStyleManualDimensioningCDDAutomaticDimensionPlacementChapterReviewQuestionsChapterExercises

ISOMETRICDRAWINGS

IntroductionIsometricProjectionandScaleTypesofIsometricDrawingsConstructingIsometricArcsandCirclesConstructionTechniquesforIsometricDrawingIsometricAnnotationsApplicationsofIsometricViewsDimetricandTrimetricProjectionsChapterReviewQuestionsChapterExercises

WORKINGDRAWINGS

IntroductionElementsofWorkingDrawingsComponentDetailDrawingsStandardPartsAssemblyWorkingDrawingsCheckingDrawingsSpecificationDocumentsWorkingDrawingSetChapterReviewQuestionsChapterExercises

APPENDIXI:A1.1A1.2A1.3A1.4A1.5

APPENDIXII:A2.1A2.2A2.3

APPENDIXIII:

APPENDIXIV:A4.1A4.2

SCREWFASTENERSScrewFeaturesStandardThreadsandThreadProfilesThreadSeriesThreadClassesThreadSpecification

GENERALTOLERANCINGANDDIMENSIONING

SymbolicSpecificationValueSpecificationHole-BasisorShaft-BasisFitSystems

GEOMETRICTOLERANCINGANDDIMENSIONING

SURFACETEXTURESurfaceTextureSpecificationSurfaceRoughnessProduction

BIBLIOGRAPHY

ABOUTTHEAUTHOR

INDEX

Figure1.1.Figure1.2.Figure1.3.Figure1.4.Figure1.5.Figure1.6.Figure1.7.Figure1.8.Figure1.9.Figure1.10.Figure1.11.Figure2.1.

Figure2.2.Figure2.3.Figure2.4.Figure2.5.Figure2.6.Figure2.7.Figure2.8.Figure2.9.Figure2.10.

Figure2.11.Figure2.12.

LISTOFFIGURES

Drawingsheetorientations.Sheetlayoutelements.Asimplebillofmaterials.Verticalcharacters.Inclinedcharacters.DrawingwithtolerancesLeader,balloon,andcallout.Samplesoffonts.Linestyles.Drawingviewwithdifferentlinestyles.Useofcenterlineandcentermark.Basictypesofprojection.(a)Parallelprojection.(b)Perspectiveprojection.Normalfaces.Non-normalfaces.Planarandobliquefaces.Boundingboxandprincipaldimensions.Imageboxandobject.Objectviewsonprincipalplanes.Imageboxfacesandprincipalplanes.Layoutofsixprincipalviewsonflatpaper.Spatialandplanarquadrants.(a)Spatiallayout.(b)Planarlayout(Rightview).Firstangleprojection.Thirdangleprojection.

Figure2.13.Figure2.14.Figure2.15.


Figure2.18a.Figure2.18b.Figure2.19.

Figure2.20.

Figure2.21.

Figure2.22.Figure2.23.Figure2.24.Figure3.1.Figure3.2.Figure3.3.Figure3.4.Figure3.5.Figure3.6.Figure3.7.Figure3.8.Figure3.9.Figure3.10.Figure3.11.Figure3.12.Figure3.13.Figure3.14.Figure3.15.

U.S.standardviews.Europeanstandardviews.Principaldimensionsanddrawinglayout.(a)Objectprincipaldimensions.(b)Layoutofstandardviews.Nonuniquesideviews.Placementandalignmentofmultiviews.(a)Correctplacementandalignment.(b)Topviewnotaligned.(c)Frontviewnotaligned.(d)Rightviewnotaligned.Object.Boundingbox.Frontviewchoice,localaxes,andviewdirections.(a)Frontviewchoice.(b)Axesandviewdirections.Viewlayout.(a)Topandfrontviews’boundaries.(b)Boundingblocksforviews.Developmentofviews.(a)Visiblefeaturesdevelopment.(b)Hiddenfeaturesdevelopment.Completedviews.Generatedviewsofacomponent.Plainmultiviewdrawing.Inclinedandobliquefaces.(a)Inclinedface.(b)Obliqueface.IdentifyingorcreatingaTLline.(a)Inclinedface.(b)Obliqueface.Anauxiliaryimageboxandlayout.(a)Imagebox.(b)Layout.Typesofauxiliaryviews.(a)Full.(b)Partial.Twoprincipalviews.Projectionlinesforauxiliaryview.Drawoutlineofface.Drawthefeature.Principalviews.TLlineandprojectionlines.Referencelineandedgeview.Projectionfromedgeview.Drawoutlineofanobliqueface.Drawfeature(s)onanobliqueface.Principalviews.

Figure3.16.Figure3.17.Figure3.18.Figure3.19.Figure3.20.Figure4.1.Figure4.2.

Figure4.3.Figure4.4.Figure4.5.Figure4.6.Figure4.7.

Figure4.8.Figure4.9.Figure4.10.Figure4.11.Figure4.12.

Figure4.13.Figure4.14.Figure4.15.Figure4.16.Figure4.17.Figure4.18.Figure4.19.Figure4.20.Figure4.21.Figure4.22.Figure4.23.Figure4.24.Figure5.1.

Fullauxiliaryview.Standardview.Edgeviewfrombaseview.Fullauxiliaryviewforanobliqueface.Partialauxiliaryandstandardviews.Conceptofsections.(a)Standardviews.(b)Mixedviews.Cuttingplanelinestyles.(a)Thickcenterline.(b)Thickphantomline.(c)Brokenvisibleline.Hatchpatternlayout.Assemblyhatchpatterns.(a)Materialtypehatchpatterns.(b)Materialtypehatchpatterns.Sectionviewrepresentation.(a)Right.(b)Wrong.Placementofsectionviews.(a)Topsectionview.(b)Frontsectionview.(c)Rightsectionview.Straightsectionview.Offsetsectionview.Removedsectionviews.Revolvedsectionviews.Alignedsectionviews.(a)Componentwitharms.(b)Componentwithoutarms.Halfsection.Brokensection.Detailsectionview.Auxiliarysectionview.Assemblysectionview.Un-sectionedfeatures.Hatchingun-sectionedfeatures.Un-sectionedparts.Breaklinesfordifferentshapesandmaterials.Constructingaregularsection.Constructinganalignedsection.Generatingasectionfromsolidmodel(SectionA-A).Dimensionalelementsandterminators.(a)Elementsofadimension.(b)Dimensionlineterminators.

Figure5.2.Figure5.3.Figure5.4.Figure5.5.Figure5.6.Figure5.7.



Figure5.17.Figure5.18.Figure5.19.Figure5.20.Figure5.21.Figure5.22.Figure5.23.Figure5.24.Figure5.25.Figure5.26.Figure5.27.Figure5.28.Figure5.29.Figure5.30.Figure5.31.

Dimensionedcomponent.Typesofdimensions.Spacingofdimensions.Arcdimensions.Circledimensions.Dimensioningdiameters.(a)Diameteronprofileview.(b)Sectionviewshowingdiameter.(c)Multiplediametersonprofileview.Angulardimensions.Holedimensions.Dimensioningslots.(a)Fulllength.(b)Lengthbetweencenters.(c)Slotwidth.Filletsandrounds.Filletsandroundsonacomponent.Chamfers.(a)External.(b)Internal.Dimensioningcounterbore,countersink,andspotface.Keyseatandkeyway.(a)Regularkeyseat.(b)Woodruffkeyseat.(c)Sledgerunnerkeyseat.Rectangularneck.(a)Depthspecified.(b)Diameterspecified.Circularneck.(a)Depthspecified.(b)Diameterspecified.Truncatedconicalneck.(a)Depthspecified.(b)Diameterspecified.Repeatedfeatures.(a)Lineararray.(b)PolararrayDatumdimensioning.Chainmethod.Tabularmethod.Engineeringdiagramofacomponent.Addinghorizontaldimensionstodiagram.Addingverticaldimensionstodiagram.Addingcircledimensionstodiagram.Generatedviewsofacomponent.Addcenterlinestogeneratedmultiviews.Addingdimensionstomultiviewdrawing.Dimensionedmultiviewdrawing.

Figure6.1.

Figure6.2.Figure6.3.Figure6.4.Figure6.5.

Figure6.6.Figure6.7.Figure6.8.Figure6.9.

Figure6.10.






Isometricprojection.(a)Isometricrotations.(b)Isometricaxesinimageplane.(a)Typesofisometriclines.(b)Isometricscale.Typesofisometricdrawings.(a)Regular.(b)Reverse.(c)Long-axis.Isometricarcs.(a)Constructingtopisocircle.(b)Constructingtopisocirclescontinued.Constructingaleftisocircle.Constructingarightisocircle.Constructingtopisocircle.(a)Boxmethodfornormalfaces.(b)Boxmethodfornormalfacescontinued.(a)Boxmethodforinclinedface.(b)Boxmethodforinclinedfacecontinued.Boxmethodforobliqueface.Boxmethodforangles.Boxmethodforellipseoninclinedface.Boxmethodforirregularcurve.Centerlinemethodforisometricdrawing.Isometricannotations.(a)Aligneddimensionplacement.(b)Horizontaldimensionplacement.Iso-detaildrawings.Isometricsectionviews.(a)Straightsection.(b)Halfsection.(c)Brokensection.(d)Offsetsection.Assemblyisometricviews.(a)Outline.(b)Exploded.Examplesofisoplanesinotheraxonometricprojections.(a)Dimetric.(b)Trimetric.Aniso-insertinanortho-detaildrawing.Standardprojectionsymbols.(a)Firstangle.(b)Thirdangle.Standardorthographicprojections.(a)Isometric.(b)Firstangleprojectionlayout.(c)Thirdangleprojectionlayout.Mixedviewsdetaildrawing.Isometricassemblydrawings.(a)Outlineisometric.(b)Explodedisometric.(c)Halfsectionisometric.


Figure7.8.Figure7.9.Figure7.10.Figure7.11.Figure7.12.Figure7.13.Figure7.14.Figure7.15.FigureP7.1.FigureP7.2.FigureP7.3.FigureA1.1.FigureA1.2.FigureA1.3.FigureA2.1.FigureA2.2.FigureA2.3.FigureA3.1.FigureA4.1.FigureA4.2.FigureA4.3.FigureA4.4.

ExplodedisometricassemblywithBOM.Sectionassemblydrawings.(a)Outlineortho-viewofassembly.(b)Frontortho-viewsection.Explodedassemblydrawing.Shaftdetaildrawing.Flangedetaildrawing.Pulleydetaildrawing.Geardetaildrawing.Retainerdetaildrawing.Sleevedetaildrawing.Scheduleofpurchaseparts.ComponentdrawingsofFigureP7.1.ComponentdrawingsforFigureP7.2a.ComponentdrawingsforFigureP7.3a.Threadnomenclature.(a)Externalthread.(b)Internalthread.Metricthreadspecifications.Englishthreadspecifications.Unilateraltolerancespecification.Bilateraltolerancespecification.Limitsspecification.ExamplesofGD&T.Elementsofsurfacetexture.Fullspecificationofsurfacetexture.Basicspecificationofsurfacetexturesymbol.Applicationexample.

Table1.1.Table1.2.Table1.3.Table1.4.Table2.1.Table5.1.Table5.2.Table5.3.TableA1.1.TableA1.2.TableA1.3.TableA1.4.TableA2.1.TableA3.1.TableA4.1.

LISTOFTABLES

SomeANSI/ASMEY14standardsSomeISOdrawingstandardsDrawingunitsStandardpapersizesPrincipalviewsanddimensionsCommondimensioningsymbolsValuesofdimensionsSomedimensionstyleattributes(AutoCADapplication)MetricthreadclassesEnglishthreadclassesInterpretingmetricthreadspecificationInterpretingEnglishthreadspecificationPreferredfits(ANSIB4.2)GD&TsymbolsTypicalsurfaceroughnessheightforsomemanufacturingprocesses

PREFACE

Thetechnicaleducationalenvironmenthaschangeddramaticallyinthelastfewdecades.Instructorsandstudentsindesigntechnology,engineeringtechnology,engineering,andrelateddisciplinesare facedwith limitedstudy time,butwithincreasing information for training in technical graphics. Contact hours forlecturesandlaboratoriesintechnicalgraphicshavebeenshrinking,butproductdesign continues togrow in complexities, and the time tomarket continues toshrink! New design tools that are largely computer based come into theworkplaceatastonishingspeed.Therearemorematerialstocover,butinfewercontact hours. These challenges need serious considerations, and this book iswrittentoaddressthem.

InstructorsarefreetouseanyCDDpackageoftheirchoicetoimplementtheconceptsandprinciplesdiscussedineachchapter.Theymayfirstgivealectureon the chapter andask the students to answer the chapter reviewquestions.Aquizonthechaptercanbecreatedandadministeredbytheinstructorbeforethechapterexercisesareattempted.Analternativeapproachistoassignachapterasa reading assignmentwith the students required to answer the chapter reviewquestionsbefore the lecture.Aquizcan thenbeadministeredafter the lecture.These approaches should help the students to understand the “rules” beforeplayingthe“game,”thatisdoingtheexercises.Introductory EngineeringGraphics is highly condensed so as tomaximize

the use of production materials. I hope students and teachers, the primaryaudience,willfindthebookavaluableresourceandenjoyusingit.IamdeeplygratefultoMomentumPress’sdedicatedteamofreviewersfortheirprofessionalcritique and invaluable suggestions.Many thanks to the hundreds of studentswhohavetakenmydraftingcoursesfortheirsuggestionsandcritiquesovertheyears. Please feel free to inform me of any error found and comment(s) forimprovementwillbehighlyappreciated.Allcommunicationsshould,please,bechanneledthroughthepublisher.

EdwardE.OsakueApril,2018.

1.1

CHAPTER1

GUIDELINESFORDRAFTING

INTRODUCTION

Drafting is the process of creating technical drawings consisting of two-dimensional (2D) images and annotations, and the termdraughting is used todescribe the language of drafting in this book. Draughting defines theterminology, symbology, conventions, and standards used in drafting. It is theuniversaltechnicallanguagethatisusedforclearlyandaccuratelydescribingtheform, size, finish, and color of a graphic design model for construction orrecording. Draughting guidelines deal with standards and conventions indrawing media, lettering, linestyes, projection standards, plot scales,dimensioning rules, sectioning rules, and so on. In this chapter, we willconcentratemainlyondrawingmedia,lettering,andlinestyles,whileotherswillbediscussedintheappropriatechapters.

The 2D images in drafting are constructed from lines and curves, whileannotations are composed from characters. 2D technical drawings may becreatedusingaxonometricandperspectiveprinciples.Axonometricdrawingsare2D drawings obtained by applying orthogonal projection principles to three-dimensional (3D) objects and include orthographic, isometric, dimetric, andtrimetric drawings. Pictorial drawings such as isometric and perspectivedrawings mimic 3D objects in appearance, but are made of 2D entities bycomposition. Most technical drawings are of the orthographic and isometrictypes,whicharethefocusofthisbook.Somestandardsandconventionsapplyto both lines and characters in drafting, and they must be learned and usedcorrectly.Therefore,draftingskillsinvolvelearningtocorrectlyapplytherulesof draughting in creating acceptable or industry standard technical drawings.Proficiency in drafting involves being able to create high-quality technical

1.2

1.2.3.4.5.6.7.8.9.10.

drawings, therefore, becoming proficient in drafting must be a commitmentexecutedwithdeterminedeffort.

CONVENTIONSANDSTANDARDS

Draughting principles, conventions, rules, and standards help to minimizemisinterpretations of drawing contents and eliminate errors in thecommunication of technical ideas. Conventions are commonly acceptedpractices, methods, or rules used in technical drawings. Standards are sets ofrulesestablishedthroughvoluntaryagreementsthatgoverntherepresentationoftechnical drawings. Standards ensure clear communication of technical ideas.Thedesigndraftermust studyandunderstand theseconventionsandstandardsand learn to apply them correctly in practice. For example, good technicaldrawingsareachievedbyfollowingsomeprinciplessuchas:

Keepingalllinesblack,crisp,andconsistent.Usingdifferentlinestyles.Ensuringclarityinlinestyledifferencessuchasinthicknessorlineweight.Ensuringdasheshaveconsistentspacingwithdefiniteendpoints.Keepingguideorconstructionlinesverythin.Ensuringthatcornersaresharpandwithoutoverlapindrawingviews.Placingdimensionwiththoughtfulnessandadequatespacing.Makingnotessimpleandconcise.Makingdrawingreadabilityahighpriority.Ensuringapleasingdrawinglayout.

Principlesone to six are largelybuilt into computer designdrafting (CDD)softwareorpackages.ThismeanstheCDDoperatorneednotworryaboutthem,except knowwhat linestyle to use for different features of objects and assignappropriate line weight or thickness. However, principles 7 to 10 must bemasteredandconsistentlyapplied.Thesehavebearingsonaccuracy, legibility,neatness,andvisualpleasantnessofdrawings.

There arenational and international organizations that develop andmanagethe development of standards. Examples are theAmericanNational StandardsInstitute(ANSI)andtheInternationalStandardizationOrganization(ISO).ANSIisafederationofgovernment,privatecompanies,professional,technical,trade,labor, and consumer organizations that serve as a clearinghouse for nationallycoordinated voluntary standards. The standards may deal with dimensions,

rating, test methods, safety and performance specifications for equipment,products and components, symbols and terminology, and so on. Majorcontributors to ANSI standards include American Society of MechanicalEngineers (ASME), Institute of Electrical and Electronic Engineers (IEEE),AmericanSocietyforTestingMetals(ASTM),andsoon.DraftingstandardsarespecifiedinANSIY14documents,whichgiveonlythecharacterofthegraphiclanguage. It is to contain 27 or more separate sections when completed.ANSI/ASMEY14.2, Y14.3, andY14.5M are popular draughting standards intheUnitedStatesandsamplesectionsofthestandardaregivenTable1.1.

Table1.1.SomeANSI/ASMEY14standards

Item Section

Sizeandformat Y14.1

Letteringandlinestyles Y14.2

Projections Y14.3

Pictorialdrawings Y14.4

Dimensioningandtolerancing Y14.5M

Screwthreads Y14.6

Gears,splines,andserrations Y14.7

Mechanicalassemblies Y14.14

ISO is a nongovernmental worldwide body that coordinates standardsdevelopmentprocessinvirtuallyeveryareaofhumanactivities.ItislocatedinSwitzerlandandwasfoundedin1947.Membershipincludesover150countries,witheachcountryrepresentedbyonenationalstandardsinstitution.ANSIistheU.S.representativetoISO.ANSIstandardsareusuallysimilarbutnotidenticaltoISOstandards.Thedesigndraftermustbediligentinadheringtothestandardsthat are relevant to a particular work. Table 1.2 gives some ISO drawingstandardsdocuments.

Table1.2.SomeISOdrawingstandards

Item Section

Technicaldrawings:sizesandlayoutofdrawingsheets ISO5457

Technicaldrawings:generalprinciplesofpresentation ISO128

Technicaldrawings:methodsofindicatingsurfacetexture ISO1302

Generaltolerances ISO2768

1.3

1.3.1

1.3.2

DRAWINGUNITS

Allengineeringdrawingsmustcarryaunitofmeasure.Thisisrequiredsothatthedrawingsizescanbecorrectlyinterpreted.Becausegraphicshavelinearandangular attributes, the units of length and angles are indispensable in draftinganddesign.

UNITSOFLENGTH

TheSIunitoflengthisthemeter.TheEnglishorU.S.customaryunitoflengthis the foot (ft). Table 1.3 shows the length denominations for SI and Englishunits.English units are still in use inNorthAmerica, especially in theUnitedStates.

The SI linear unit for drafting is the millimeter. Mechanical drawings aredimensionedinmillimeter(mm).Architecturaldrawingsmaybedimensionedinmillimeter (mm) and meter (m).Meter and kilometer (km) are used for civildimensioning.Onlydecimalsareusedinmetricdimensioning;fractionsarenotallowed.Fornumberslessthan1.0,whichmustbeexpressedasdecimals,azerobeforethedecimalmarkerispreferred.Forexample,0.234ispreferredto.234.Theperiodsymbolis thedecimalmarkerinthisexample.InEuropeandsomeother countries, “,” is used as decimal marker, i.e. 0,234 means the same as0.234inNorthAmerica.

In English units, mechanical drawings are dimensioned in decimal inches,architectural drawings are commonly dimensioned in feet (‘), and fractionalinchesandcivildrawingsaredimensionedindecimalfeetandinches.InNorthAmerica,drawingsinmetricunitscarryageneralnotesuchas“alldimensionsareinmillimeter,unlessotherwisestated”orthelabel“METRIC.”

Table1.3.Drawingunits

SI:meter(m) Customary:Inch(in)-foot(ft)

1m=1,000mm=103mm 1in=16lines

1m=100cm=102cm 1ft=12inches

1km=1,000m=103m 1in=25.4mm

UNITSOFANGLE

Angle refers to the relative orientation of lines on a plane or the relative

1.4

orientationofplanes in spaceand ismeasured indegrees (°)or radians.Thereare360degreesinacircle;60minutesinadegree;and60secondsinaminute.TheradianistheSIunitofangularmeasure.Oneradianisapproximately57.3°.However,thedegreeistheunitofangularmeasureintechnicaldrawings.

DRAWINGMEDIA

Drawing media are physical materials that can retain graphic and textualinformationforareasonabletimeperiodwhenplacedontheirsurfaces.Theyareused to produce hard or paper copies of models and drawings. Certaincharacteristicsmakethesemediasuitablefordrawingsandincludesmoothness,eraseability,dimensionalstability,transparency,durability,andcost.Smoothnessdescribes the ease of the media to accept lines and letters without excessiveeffort.Eraseabilitydescribestheeaseofthemediatoallowlinesandletterstobeerased and cleaned-up.Ghosting is a termused todescribe themark left afterlines are erased. The more visible they are, the poorer the eraseability.Dimensionalstabilityreferstotheabilityofthemediatoretainsizeinvaryingweatherconditions.Transparencyallowsdrawingsononesideof themedia tobe visible on the other side. This used to be an important characteristic intraditionaldrafting,butphotocopying technologyandplotter capabilities todaymakethisrequirementanoncriticalfactor.Durabilityreferstotheabilityofthemediatoresistnormalusagewearandtear.Wearandteariseverpresentbecausewrinklesdevelopwithusagethatrenderdrawingsdifficulttoreadorreproduce.Drawingmediaincludebondstationary,vellum,mylar,gridpapers,andtracingpapers.Bond stationary or plain paper is good for all types of technical drawing.

Theyaremadefromwoodpulpofhigherqualitythannewsprint.However,theyhavelowdurability.Therearedifferentgradesofplainpaperinthemarket.Thebetteronesarewhiterandsmoother.Plainpapersshouldbepreferablyusedforsketches,exploratorydesigndrawings,andcheckprints.Vellum is themostpopulardraftingpaper. It is speciallydesigned toaccept

pencilmarksandink.Ithasgoodsmoothnessandtransparency,butsusceptibleto humidity and otherweather conditions.Thismakes it not to be very stabledimensionally.Somebrandshavebettereraseability.Mylar is a plastic type (polyester) drafting material that has excellent

dimensional stability, eraseability, durability, and transparency. It takes inkeasily,butitisexpensiveandrequiresspecialpolyesterleadfordrawingonit.Itis,thus,usedforveryhigh-qualityjobsorwhencostisnotafactor.Mylarmay

1.4.1

1.4.2

have single or doubleworking (mat) surfaces.The singlemat surface ismorecommon.Tracingpaperisatranslucentmediumthatisgoodwhentheneedtoreduce

manual repetitive work is considerable. It can also be used to obtain a finalsketchiftheoriginalsketchwasdrawnonagridpaper.Thegridbackgroundisnottracedinthiscase.Tracingisafastandaccuratemethodofreproducinganexistingdrawingmanually.Gridpapers areespeciallyhelpful forgoodalignmentandproportioningof

features on drawings when sketching. Advantage should be taken of themwhenever available.The squaregrid is used for sketchingorthographic views,andisometricgrid isusedforsketchingisometricviews.Thesegridpapersareverycommon.

DRAWINGSHEETORPAPERSIZES

PaperorsheetsizeshavebeenstandardizedbyANSIandISO.Standarddraftingpapers are available in sheet or roll form. Table 1.4 summarizes the standardpaper or sheet sizes for English (ANSI) and metric (ISO) applications withmetric as preferred units. The sizes are the overall dimensions of the sheetswithoutallowanceformargins.RollsheetscomeindifferentwidthsandlengthswiththewidthusuallyequaltooneofthestandardsheetdimensionsasshowninTable1.4.Metric roll sizes vary from 297 to 420mm inwidth. Largemetricsheet sizes are cut frommetric rolls. Roll sizes in English unit vary inwidthfrom18”to48”,andtheusuallengthofarollis100’long.InEnglishunit,largesheetsizesF,G,H,J,andKarecutfromrolls.Inmostsituations,thepapersizeisspecifiedbythecompanyorstatedinagivenproblem.

Table1.4.Standardpapersizes

Metricsizes(mm) Englishsizes(inches)

A4 210×297 A 8.5×11

A3 297×420 B 11×17

A2 420×594 C 17×22

A1 594×841 D 22×34

A0 841×1189 E 34×44

SHEETORIENTATION

1.5

Standard drawing sheetmay be orientedwith the long-side horizontal and theshort-sideverticalasshowninFigure1.1a.Thistypeoforientationisknownaslandscape and is generallypreferred for sheet sizesB,C,D, andE inEnglishunit or sheet sizes A3, A2, A1, and A0 in metric unit. Occasionally, portraitorientation, as shown in Figure 1.1b, is used, but is largely limited to A-sizesheet inEnglishunit andA4-size sheet inmetricunit. In this layout, the shortlengthofthesheetishorizontalandthelongsideisvertical.

Figure1.1.Drawingsheetorientations.

SHEETLAYOUT

Drafting paper layout refers to the arrangement of information on the paper.Figure1.2 shows the general layout of a template drawing sheet.Broadly, theinformation in a drawing sheetmaybe classified into twogroups of technicaland administrative. The technical information consists of drawing views andannotations.Annotationdependson theamountofdetailsdesired inadrawingand may include dimensions and tolerances, notes, and bill of materials inassemblydrawings.The technical informationusually takes thegreaterportionof the drawing sheet.Administrative information on a standard drawing sheetincludestitleblockandrevisionblockinformation.Amarginisprovidedatthefouredges(top,bottom,left,andright)ofthesheetandisdefinedbytheborderline (not shown in Figure 1.2) that is drawn at some distance from the edge.They provide spaces for filing and handling the sheet. Based on ANSIrecommendations, top,bottom,and right-sidemarginsare in the rangeof12.5mm(1/2”)to25mm(1”),dependingonthepapersize.Theleft-sidemarginisoftenbetween12.5mm(1/2”)to40mm(1–1/2”)toallowforbindingofsheets.

1.5.1

1.5.2

1.2.3.4.5.6.

Drawingviews depend on the type of documentation required, and annotationcontentwillvaryaccordingly.

ZONING

Zoning is a technique used in large paper sizes to aid in quickly locatinginformationonadrawing.Itinvolvesassigningspacednumbersonthetopandbottommargins of a sheet and spaced letters on the left and rightmargins asshown in Figure 1.2. This creates a grid system on the drafting paper that issimilar to thatusedfor reading informationonmaps.Azone isdefinedby theintersectionofalettersegmentandanumbersegment.Asazoneisaverysmallsection of the drawingpaper, locating a piece of information in it is fast.ThehatchedblockinFigure1.2isforzoneB3.

Figure1.2.Sheetlayoutelements.

TITLEBLOCK

ByANSIstandard,a titleblockshouldbe locatedon the lower-rightcornerofthedrawingsheet.Thoughdifferent titleblockdesignsareusedbycompanies,the informationcontained in them is fairlygeneral.Most information ina titleblockincludes:

Company:name,address,phonenumber.Project/Client:projectnumberandtitleorclient’snameandaddress.Drawing:nameortitleornumber.Personnel:designer,drafter,checker,approver.Scale:ratioofdesignanddrawingsizes.Date:completiondateofdrawingorproject.

7.8.9.10.

1.5.3

1.5.4

Sheet:sizeandnumber(page)ofsheetsindrawingset.Revisionsblock:ablockforrevisionnotes.Generaltolerance:toleranceappliedtoasizewhenunspecified.Projectiontypesymbol:firstorthirdangle.

BILLOFMATERIALS(BOM)

Anassemblydrawingshouldhaveabillofmaterials (BOM)orparts list. It isusuallyatablelistofthepartsorcomponentsinanassembly.Figure1.3showsasampleofasimpleBOM.ByANSIstandard,itshouldbelocatedonthelower-rightcornerofthedrawingsheet.ImportantinformationinBOMispartname,itemnumber,partmaterial,quantity,partnumber,orcatalognumberforstandardparts.The itemnumber is thenumber assigned to a component in aparticularassemblydrawing,a formof local identificationandcanchangewithdifferentassemblydrawings.Thepartnumberisafixednumberassignedtothatspecificcomponent, a formofcompanyorglobal identificationand shouldnot changefordifferentdrawings.Otherinformationlikeweightandstocksizemayalsobeincludedinthepartslist.

Figure1.3.Asimplebillofmaterials.

REVISIONBLOCK

ArevisionblockisofthesameformatasaBOM,buttrackschangesmadeona

1.6

1.2.3.4.5.

1.6.1

componentorassemblydrawing.Itisoftenlocatedonthetopright-handcornerof thedrawingsheetadindicatedinFigure1.2.Changesonworkingdrawings(prototypeandproductiondesigndrawings)mustbeapproved,soeachcompanyusually has a documentation process in place that must be strictly followed.Preliminarydesigndrawingsmaybechangedwithoutfollowingthisprocess,butwiththeapprovaloftheengineerordesigner.Someoftheinformationitemsinarevision block may include date, change reason, requester, previous and newsizes,andapprovedby.

ANNOTATIONS

The textual information and symbols added tomodels and drawing views forcomplete documentation of design are commonly called annotations. Whenannotationisdonemanually,itiscalledlettering,whichusedtobeatediousandtime-consuming task.But, things arequitedifferentnowwith computers; theyhave greatly increased the speed and quality of lettering. Text informationconsists of groups of characters that expressmeaning,which could bewords,phrases, and or sentences. In technical graphics, the aim is to communicateclearly and legibly so as to avoidmisinterpretationof intent andpurpose.Thefactorsthatcangreatlyaffectlegibilityare:

FontCharactersize(textheight)CharacterspacingWordspacingLinespacing(leading)

LETTERINGCONVENTIONS

Charactershavedifferentmodeldesignsknownasfonts.Afontisasetorfamilyofcharacterdesignwithspecificattributesthatdeterminetheprintappearanceofthe characters. The attributes hold the information about the character set.Simplerfontstylesareeasiertoread;therefore,openclean-cutcharactersarethebestfordrafting.ANSIstandardfontforletteringintechnicalgraphicsissingle-strokeGothicfont.Eachcharacterinthisfontismadeupofasinglestraightorcurved lineelement.Thismakes iteasy todrawthecharactersandmake themclear to read. There are uppercase, lowercase, and inclined Gothic letters.However,theverticalGothiclettershavebecomeindustrystandard.Figure1.4a

shows vertical uppercase letters, Figure 1.4b shows numbers, and Figure 1.4cshowslowercaselettersandproportion,andhoisthesymbolfortextorcharacterheight in the figure. Characters in annotations may be inclined from thehorizontalatanangledefinedby5/2(riseoverrun),approximately68degreesperANSIasshowninFigure1.5.

Figure1.4.Verticalcharacters.

Figure1.5.Inclinedcharacters.

Animportantattributeofafontisthetextheightorfontsize.Textheightismeasuredinlinearunitofmm(inch).TheANSIrecommendedtextheightis3mm(1/8”).Thewidthofcharactersvariesdependingonthespecificfont.Somecharacters are narrow like I and others wide likeW. The ratio of a characterheighttothewidthisdescribedaswidthfactororaspectratio.Commonaspectratios forcharactersare5/6,1,and4/3.Thespacingbetweenwordsshouldbeapproximatelyequalandaminimumof1/16”(1.5mm)isrecommended.Afullcharacterheightforwordspacingispreferred.Thespacingbetweenlinesshouldbeatleasthalfthetextheight,butpreferablyafulltextheight.Sentencesshouldbe separated by at least one text height; however, if space allows, two textheightsshouldbeused.

Annotationinformationmaybedividedintotwocategoriesoftechnicalandadministrative information.Administrative information includes revision notesandtitleblock.Revisionnotesareusedfordocumentcontrolandrecord-keepingof changes in design. The title block contains vital information about thecompany and the drawing. Technical information includes BOM, dimensions,notes, and specifications. Dimensions are the size values of objects, andtolerances are permissible variations on object sizes.The sizes and tolerances

shownondrawingviewsmustbethefunctionalordesignsizesandtolerancesasspecifiedbytheengineerordesigner.InFigure1.6,thediametersizeof20mmhas a tolerance of 0.05 mm. Annotation symbols are commonly used forgeometric tolerancing and dimensioning (GD&T). Notes are explanatory orrequired informationneededonmodelsanddrawings forproper interpretation.Therearetwotypesofnotesfoundindrawings:generalandlocalnotes.Generalnotesapplytothewholedrawingandmaybeplacedinthetitleblockoratthebottomofadrawingviewarea.Localnotesapplyonlytoaportionorspecificfeaturesinadrawingandareplacedclosetothefeaturereferenced.Aleaderlinecanlinkalocalnotetoafeatureorportionofadrawing;calloutsandballoonsarespecialformatsofplacinglocalnotes.Figure1.7showsexamplesofaleader,balloon, and callout. Balloons are local notes placed inside a shape (circle,diamond,etc.).Calloutsarelocalnotesplacedwithoutashape.Notesshouldbemade simple and concise. Specifications are technical requirements and areusually about material type, processing, and finishing. They often appear asgeneral notes or are put together as separate documents. Leader lines are thincontinuouslinesusedtodirect informationtospecificfeatures inadrawing.Aleaderlinehasanarrowhead,aninclinedsegment,andahorizontalsegmentasatail.Theinclinedsegmentconnectsthearrowheadwiththehorizontalsegment.

Figure1.6.Drawingwithtolerances

Figure1.7.Leader,balloon,andcallout.

Annotation in CDD is much easier than lettering. CDD letters are neat,consistent,stylish,andcanbecreatedwithspeedandaccuracy.Manyfontsareavailable in the CDD software, so there is a tendency to use several fonts inCDDlettering.However,thisshouldbelimited,perhapstotwoorthree.Figure1.8 shows a sample of fonts. In architectural drawings,Country blueprint andCityBlueprint are popular fonts,while Simplex font is popular inmechanicaldrafting. Placing text in CDD drawings requires decisions on text height andinclinationangleattheleast.Theinclinationangleoftextis90°bydefault,butthis could be changed. The recommended inclination angle is about 68°. Thepositionofthetextisoftenselectedbyclickingwithamouse.Textalignmentorjustification is important in CDD lettering because it affects documentappearanceandreadability.Textcanbealignedtotheleft(leftjustified),alignedtothecenter(centerjustified),oralignedtotheright(rightjustified).Textsthatare aligned on both left and right edges are referred to as fully justified. Intechnical notes, text should be left justified.Character,word, and line spacinghavebeendiscussedearlierandinCDDpackages;theyhavedefaultsettingsthatmay be changed if desired. Fonts can be formatted by applying differenttreatmentslikebold,italic,andunderline.Thesearecalledspecialeffects.Theyaddaestheticsandemphasistoannotations.

Theplotheightofacharacteristheactualsizeonaprintedsheetandmaybesmallprint,normalprint,orlargeprint.NormalprintistherecommendedANSItextheightof3mm(0.125”).Normalprintisusedwithinthedrawingviewsareaandworks fine for average-sized sheets such asA4 (A-size) andA3 (B-size).Dimensions, notes, and specifications should be printed in normal print orstandard height. Small prints are smaller than the normal prints and are usedwhenspaceislimited.Theymayvaryinheightfrom1.5to2.5mm.ItisoftenusedinrevisionblocksandpartlistsorBOM.Plotheightinlargeprintscanvaryfrom5 to 10mm (0.188” to 0.375”).They are used for headers, viewnames,titles, labels, andnumbers in titleblocks.For large-sized sheets, textheightof0.175to0.25”(5–6mm)iscommon,butmaybeashighas0.375(10mm).Textheightforzonelettersandnumbersisusuallylargerthanthosefordimensionsortolerances.Uncrowded text (high aspect ratio) is easy to read, but needsmore

1.7

space than crowded text (small aspect ratio). Some companies may prefercrowdedtexttouncrowded;however,cleanandeasy-to-readannotationsshouldbe the goal. It is good practice to find out what the convention is in yourcompanyandsticktoit!Thedesigndraftermustchooseaplotsizethatislegibleandcomfortabletoreadwhenhardcopiesaremade.Smallplotsizestendtobehardontheeyesandshouldnormallybeavoided.

Figure1.8.Samplesoffonts.

InCDDsituations,therearetwoaspectsoftextheight:plotsizeandscreensize. The plot size is the actual text height value on a printed or plotteddocument. ANSI-recommended plot size for small sized drawings is 3 mm(0.125”). The screen text size in CDD is the text display size on themonitorscreenofthecomputer.ThismaybedifferentfromtheplotsizeifadrawingisnotfullscaleinthedefaultworkspaceofaCDDpackage.Inthiscase,ascreenscalefactormustbeapplied to thedesiredplotsizeforcomfortablereadingorviewingon the screen.The screen text height is theplot size times the screenscale factor in reduction scalingwhere the image plot size is smaller than theimage design size. The screen text size is the plot size divided by the screenscalefactor inenlargementscalingwhere the imageplotsize is larger than theimagedesignsize.Reductionscalingiscommoninmacro-technologyproductswhile enlargement scaling is common inmicro- or nano-technology products.TheANSIstandardplotorprinttextheightof3mm(1/8”)workswellwithA4-size(metric)orA-size(English)sheet.Forothersheetsizes,someadjustmentintextheightmaybenecessaryforcomfortablereadingofprints.

LINESTYLES

Linestyledescribesthevisualappearanceoflinesonpapersandmonitorscreens.Drafting uses different linestyles and symbols to describe object models,especiallyindescribingdetailsof3Dgraphicsin2Dspace.Goodlinequalityisessential for accurate communication of drawings. CDD linestyles are crisp,consistent,clear,anddifferentlinethickness(orline-weight)andcolorscanbe

assigned to them. Their dashes have consistent spacing and constant width.Figure1.9showssomelinestyles.

Therearetwofundamentallinestyles,namely,continuous(solid)andbrokenlines. Continuous lines have no gaps but broken lines do. Continuous linevariantsincludevisible(object),construction,extension,andborderlines.Theselines are distinguished by thickness or width. ANSI recommends two lineweightsofthickandthin,withthethickbeingtwicethelineweightofthethin.Thicklineshavewidthgreaterthan0.3mmandthinlineshavewidthof0.3mmor less. Visible and border lines are thick, while guidelines, construction, andextensionlinesarethin.Brokenlineshavevisiblegapsbetweenconsecutivelinesegments.Thelengthofdashlinescanvaryfrom3to10mm(1/8”–3/8”),andthegapcanvaryfrom1.5to3mm(1/16”–1/8”).ThicknessoflinesandlengthofdashesmentionedherearebestforanA-sizesheet.

Figure1.9.Linestyles.

Visible (object) linesare thickcontinuous (solid) lines that representvisible

edgesoroutlinesofobject.Straightedgesareformedwheretwoplanesintersect.Curvededgesarisefromcurvedfacesandsurfaces.Visiblelinesshouldbecrispandblackwiththicknessof0.40,0.50,or0.60mm,dependingonsheetsize,butANSI-recommendedthicknessofvisiblelineis0.60mm.Hidden lines are thin dashed lines representing edges that are within the

object or behind some features, and so are not directly seen from a viewdirection. The edges are known to be physically present in an object. Hiddenlinesgenerallyhavedashlengthof3mm(1/8”)andagapof1mm(1/32”),butcan varywith sheet size or drawings. The gap is about a quarter of the dashlength.Hiddenlinesshouldstartorendatvisibleorotherhiddenlines.Nogapisallowedbetweenhiddenandvisiblelines.Centerlines are thin broken lines of alternating long and short strokes

separatedbyagap.Acenterlineisusedtoshowandlocatecentersofcirclesandarcs and to represent lines of symmetry and paths of motion in objects.Centerlinesshouldcrossvisiblelineswith3mmormorebeyondthem.Thegapandshort strokeareofequal length.Theshort stroke isaboutaquarterof thelongstroke,whichisabout10mmlong.Dimension lines are continuous thin lines used to indicate the value of a

dimension. A dimension line has three elements: the dimension value, theterminator,andthestem.Thestemisthethinlinethatendswiththeterminatorsat both ends. The terminatormay be arrows (usually filled), slashes, or filledcircles.Thedimensionvaluemaybeplacedon topof the stemorat abrokenportionofthestem.Extensionlinesareapairofcontinuousthinlinesusedtoestablishtheextent

ofadimension.Theextensionlinereferencesapointonafeaturewithasmallgap (1.5mmminimum)between thepoint and thebeginningof the extensionline. They are used in conjunction with dimension lines and slightly extendbeyond the dimension lines about 3 mm. Extension and dimension lines arealwaysperpendicular.Phantomlinesare thindashed linesused to identifyalternativepositionsof

moving paths, adjacent positions of related paths, or repetitive details. Aphantom line consists of a long dash, two short dashes, and gaps between thedashes.Gapsareabout3mmlongbutcanvary.Cuttingplanelinesareusedtoindicatethepositionanddirectionofviewfor

cuttingplanesplacedonanobjectmodeltocreatesectionviews.Theyarealsousedtoindicateauxiliaryviewplaneanddirection.Cuttingplanelinesareeitherthick phantom or hidden lines with arrow heads that are normal to the mainlines.Thearrowspointintheviewdirections.Thelongdashisaboutfivetimestheshortdash.Theshortdashandgapareofequallength.Gapsareabout3mm

1.8

1.9

longbutcanvary.Section (hatch) linesare thin inclined linesused to identifyasolidmaterial

cut through by a section plane. They form a pattern on the section affected.Sectionassemblydrawingsoftenhavecomponentsofdifferentmaterials inthesectionplane.Thedeferentmaterialsaredistinguishedbyusingdifferentanglesfor section lines in the section.Section lineanglesnormallyvarybetween15°and75°.Break lines can be either thin or thick. Long breaks are thin, while short

breaksarethick.Theyareusedtoshowthatsomeportionofanobjectisleftout.Ashortbreaklineisusedforsmallareasofinterestandallowsgreaterdetailstobe shown. Long break lines are used when space needs to be saved inrepresenting very long objects. Usually, the middle portion of the object isbrokenoffortheportionwithoutadditionalinformationisleftout.Stitchlinesconsistofaseriesofdotsandarealsocalleddotlines.Theymay

be used as projection lines or guidelines in grid papers used for freehandsketching.

PRECEDENCEOFLINESTYLES

When lines of different styles overlap or coincide in a view, some takeprecedence. Generally, lines of thicker weight take precedence over others ofthinner weight. Visible lines take precedence over all other linestyles. Thefollowing order of precedence is generally accepted: visible, hidden, cuttingplane, centerline, break line, dimension and extension lines, and hatch line. Ifmorethanonelinestylescoincideinaview,thentheruleofprecedencemustbeapplied.

APPLYINGLINESTYLES

Figure 1.10 shows a drawing view with several linestyles used in itsrepresentation. The visible, hidden, and centerline styles are perhaps themostfrequently used in drawings. Though CDD has highly simplified linestylecreation and placements, attention should be paid to the placement ofcenterlines. This is because when the length of the horizontal and verticalcenterlinesareunequaloveracircleorarc,thecentermarkforthecircleorarcwillappearunequal.Thisdoesnotgiveaneatappearanceinadrawing.Onewayto fix this is to draw the centerlines across the circle or arc diameters. Then,

scalethecenterlineswithascalefactorslightlymorethan1.0,say1.25,1.3,1.4,or1.5.

Figure1.10.Drawingviewwithdifferentlinestyles.

Figure1.11.Useofcenterlineandcentermark.

Figure 1.11 shows the use of centerlines and center marks. Note thatcenterlines must not terminate on visible lines. They should extend beyondvisiblelinesatleast3mm.Thecentermarksmaybeusedinplaceofcenterlinesin circles or arcs of small radii orwhenovercrowding of line typesmaybe aproblem. This is due to concern about drawing clarity and readability, a toppriority ingraphiccommunication.Conventionsandstandardsmustbeapplied

1.10

1.2.3.4.5.6.

7.8.9.10.11.12.13.14.15.16.17.

18.19.20.21.

1.11

toensureunambiguouscommunication.CentermarksareeasyandfasttoapplytodrawingsinCDDsystems.

Linestylemistakesused tobequitecommonwithboarddrafting.However,CDDhaslargelyeliminatedthesebecausethecodingoftheCDDsoftwarecanimplementconsistentandaccuratelineweight,linecrossing,anddisplay.But,infreehandandinstrumentsketches,effortsmustbemadetoavoidtheseerrors.

CHAPTERREVIEWQUESTIONS

Definethetermsdraughtinganddraftingasusedinthistextbook.Definethetermsconventionsandstandards.Statetheprinciplesforcreatinggoodtechnicaldrawings.WhatarethemeaningsoftheacronymsANSIandISO?WhatANSIstandarddealswithdrafting?Which section of ANSI drafting standard is concerned with dimensioningandtolerancing?Whatmeasurementunitsarefoundorusedindrafting?Listthefirstthreestandardpapersizesinmetricsystem.ListthefirstthreestandardpapersizesinEnglishsystem.WhatarethesizespecificationsofA-andA4sheets?Whatinformationisoftenshowninatitleblock?Definezoningasusedindrawingsheets.Whatisannotation?Describelettering.Whatarethetwofundamentaltypesoflinestyles?Listthreeexamplesofeachfundamentaltypeoflinestyles.Whatarethetypesoflinethicknessmentionedinthischapter?Distinguish between visible and hidden linestyles.When are they used indrawings?Whenarephantomlinesusedindrawings?Wherearecenterlinesusedindrawings?Cancenterlinesendatvisiblelines?Whencanyoureplacecenterlineswithcentermarks?

CHAPTEREXERCISES

EXERCISE1

(a)1.2.3.4.

(b)

Sketchthefollowinglinestyes:VisiblelineHiddenlineCenterlinePhantomline

Sketchtwocircles:onebigandtheothersmall.Showcenterlinesonthebigcircleandcentermarksonthesmallcircle.

EXERCISE2

UsefreehandsketchingtoreproduceFigure1.10andFigure1.11,indicatingthelinestyles.

2.1

2.2

CHAPTER2

STANDARDORTHOGRAPHICDRAWINGVIEWS

INTRODUCTION

Orthographicviewsare2Dimagesofa3Dobjectobtainedbyviewingit fromdifferentorthogonaldirections.Sixprincipalviewsarepossibleandarenamedtop,bottom,front,rear,left,andrightviews.However,threeofthesixviewsareregardedasstandardviews.TheU.S.standardviewsarethetop,front,andrightviews and are based on third angle orthographic projection. The Europeanstandard views are the front, top, and left views and are based on first angleorthographicprojection.2Dorthographicviewscanbegenerateddirectly fromsolid models, which is much faster than constructing the views. Multiviewdrawingsconsistoftwoormoreviewswithappropriateannotationsarrangedinsome preferred pattern. They include standard orthographic views, auxiliaryviews, and sectionviews.Auxiliary and sectionviews are used to supplementstandardviews inorder toclarifyviews, improvevisualizationofdesigns,andfacilitatedimensioningofdrawings.Detailcomponentdrawingsaremostoften2Dengineeringdrawingsofpartswithnecessary information for construction,manufacturing,orinspection.2Dassemblydrawingsareextensivelyusedinthebuilding of equipment and structures. Multiview drawing guidelines areprescribedbyANSI/ASMEY14.3MintheU.Sstandards.

PROJECTIONTYPES

Projection is the graphic technique of connecting points on a 3D object by

straightlines(linearprojection)topointsonanimageplanessoastocreateitsimage(s).Naturalobjectsarein3Dsolidformboundedbyvertices,edges,andfaces.Verticesarepointsonobjects,edgesarelinesonobjects,andfacesareflatandcurvedsurfacesonobjects.Theseandothergeometricentitiesthatmakethesolidarecalledfeatures.Aspointsarethemostbasicgraphicfeatures,imagesofobjectsmaybecreatedfrompointsonit.Inaprojection,pointsona3Dobjectare used to create its image(s) on a projection or picture or image plane. Theimage plane is an imaginary transparent flat surface that coincides with thedrawingsurface,whichmaybeapaperorcomputerscreen.Aprojectionrelatesan observer and an object to an image plane through the lines of sight orprojection.Inanorthographicprojection,theviewsoftheobjectareobtainedbyviewing it from different orthogonal directions. This technique allows a 3Dobjecttobeaccuratelyrepresentedona2Dplanewithmultipleviews.Therearetwo types of projections: parallel and perspective projections. Figure 2.1illustratestheprinciplesofbothparallelandperspectiveprojections.Inparallelprojection,theprojectionlinesarealwaysparallel,butinperspectiveprojection,theprojectionlinesconvergeatapoint.Whiletheobserverisinonepositioninperspective projection, several positions are needed for parallel projection.Parallelprojectionisusedinorthographic,axonometric,andobliqueprojectionmethods.Axonometricprojectionshavethreevariantsofisometric,dimetric,andtrimetricprojections.Perspectiveprojection isusedtogenerateone-point, two-point, and three-point perspective drawings. Perspective, axonometric, andoblique projections are used to generate pictorial drawings. Whether theprojectionisparallelorperspective,theimageofobjectverticesareconstructedontheimageplaneattheintersectionsoflinesofsightandtheimageplanes.

Projections are true representations of objects on appropriate scales.However,trueprojectionssometimesdistorttheviewofobjects.Hence,insomesituations,practical judgment is applied, anda representationdeviating fromatrue projection is substituted. Thesemodified projections are called drawings,notprojections.Forexample,theisometricscaleisabout18percentshorterthantrue size. For convenience, the actual dimensions of the object are shown inisometricviews,andsuchviewsare,therefore,calledisometricdrawingsandnotisometricprojections.

2.3

2.3.1

1.

Figure2.1.Basictypesofprojection.(a)Parallelprojection.(b)Perspectiveprojection.

ORTHOGRAPHICPROJECTIONCONCEPTSANDASSUMPTIONS

Anorthographicprojectionisaparalleltypeofprojectiontechniqueinwhichthelines of sight are parallel but perpendicular to the image planes.Orthographicviews or orthoviews make it possible to describe a 3D object in 2Dmultipleviews.Formanufacturingandinspectionpurposes,informationabouttheshape,size, and location for each featureonanobjectmustbepreciselydescribed toavoidproblems.Inanorthographicprojection,anobserverlooksatanobjectinaviewdirectionofinterest.Bychangingpositionsinstepsof90o,multiple2Dviewsoftheobjectcanbegenerated.Usingmultiple2Dviewsarrangedinwell-definedpatternprovideaneasymeansofadequatelydescribing3Dobjects.Withorthographic views, it is possible to completely describe the shape, size, andlocation of features on it, and hence provide precise information formanufacturingand inspection.Multiviewdrawingsarecombinationsof twoormoreorthographicviews.Oneviewoforthographicdrawingrevealsonlytwoofthe threeprincipaldimensionsofanobject.Therefore, twoviewsarenormallyrequiredinamultiviewdrawingtodefinethethirddimension.Though2Dviewsareeasiertocreate,readingandinterpretingthemrequiredraftingskillsbecausethey are abstract or conceptual form of representation. Standard orthographicviewsare2Dviewsselectedbynationalandinternationalstandardorganizationsthatareusedforformaldesigndocumentation.Theconcepts,assumptions,andprinciplesoforthographicprojectionaresummarizedbelow.

CONCEPTS

Line of sight: Direction of light travel from an observer to the object and

2.3.4.

2.3.2

1.2.3.4.5.

2.4

imageplane.Imageplane:Flatsurfacewhereimageisconstructed.Object:Abstractorrealentityofinterest.Observer:Imaginedpersonlookingatanobject.

ASSUMPTIONS

Observerisatinfinitedistancefromtheobject.Imageplanesareorthogonal.Linesofsightmeetimageplanesatarightangle.Pointsonobjectsareprojectedonimageplanes.Linesofsightarerepresentedbyprojectionlines.

OBJECTPLANESANDFEATURES

Realobjects are3D innature, so the representationofobjects in3Dgives themost realisticmodel.They are construed to consist of features,whichmaybesegmentsof2Dshapesand3Dforms.3D featurescouldbemain segmentsofbasic3Dformssuchascylinders,boxes,cones,pyramids,orauxiliarysegmentssuchasholes,screws,whicharepartofobjects.2Dfeaturesmaybebasicshapessuchas rectangles, circles, ellipses,or segmentsof shapes like lines, arcs, andpoints. Points on objects are known as vertices. Edges are lines or curves onobjectsandareformedfromtheintersectionoftwoplanesorsurfaces.Afaceisasurfaceonanobjectthatmaybeflatorcurved.Facesaredefinedrelativetoanobject,butsurfacesandplanesneednotbereferencedtoanyobject.ThereareverticalandhorizontalplanarfacesasshowninFigure2.2.Othertypesofplanarfaces are inclined and oblique faces. Figure 2.3 shows examples of planar,curved,andinclinedfaces,andFigure2.4showsexamplesofplanarandobliquefaces.

Features on normal faces of objects appear as true size and shapes in anorthographicprojection.Featuresoninclinedandobliquefacesdonotappearastrue size and shapes in an orthographic projection. They are described asforeshortened because the apparent size or shape on the projected view is notequaltothetruesizeorshape.Thetruesizeandshapeofafeatureonaninclineface isobtainedonanauxiliaryplaneperpendicular to the inclinedplane.Thetruesizeandshapeofa featureonanoblique face isobtainedonanauxiliaryplaneperpendiculartoaplanethatshowsatruelengthofaforeshortenededgeintheoriginalface.Atleastoneauxiliaryprojectionisrequiredtodevelopthetrue

2.5

sizeandshapeofafeatureonaninclinedface.Atleasttwoauxiliaryprojectionsarerequiredtodevelopthetruesizeandshapeofafeatureonanobliqueface.Thenextchapterdiscussesauxiliaryviews.

Figure2.2.Normalfaces.

Figure2.3.Non-normalfaces.

Figure2.4.Planarandobliquefaces.

BOUNDINGBOXCONCEPT

The box volume an object occupies in space is defined by its principaldimensions.PrincipaldimensionsaretheoverallsizeintheprincipalaxesofX,Y,andZin3Dspace.TheseareoftendesignatedasW,D,andH,respectively,asshowninFigure2.5.InFigure2.5,theobjectconsistsoftwo3Dsegmentsofatopcylinderandroundedboxatthebase.Theboundingbox(B-box)isindicatedwith phantom line style. In general, the bounding box of an object can be

2.6

constructed,nomatterhowcomplicated.Itgivestheminimumvolumeofaboxthat can accommodate the object. Also, it provides a natural basis forconstructingalocalorobjectrectangularcoordinatesystem.Inanorthographicprojection,projectionplanesareassumedtobeimaginary,buttheB-boxseemstobeanintuitiveframeworkforvisualizingimageplanes.Inthisregard,imageplanesassumephysicalsignificanceonthebasisofaB-box.Thisconceptseemstobeonenotpreviouslyrealized.

Figure2.5.Boundingboxandprincipaldimensions.

VISUALIZINGANORTHOGRAPHICVIEWPROJECTION

ConsideringtheB-box,theimageboxcanbeseenasanenlargedB-boxfortheobject,asshowninFigure2.6.Thus,theB-boxprovidesaconceptualbasisforconstructinganimagebox.Now,positiontheimageboxsuchthattheobjectisatthecenter.Theimageboxismadeupofsixplanarsurfaces,andthesurfacesareknown as principal planes. Consequently, six 2D images of the object can becreated.Theimageboxisconsideredtransparentsothattheobjectinsideitcanbeseenbytheobserverfromoutsidethebox.Theboxissometimescalledthepicturebox.With the imagebox inplace, theobserver ispositioned inaviewdirectionperpendiculartoanimageplane,saythefrontside,asshowninFigure2.7.Verticesontheobjectarethekeypointsusedforaprojection.Linesofsightare imagined to project or run from a vertex to a point on an image plane.Becausetheviewdirectionisperpendiculartotheimageplane,thelinesofsightwill intersect the image plane at right angles.A piercing point is the point ofintersection of a line and a plane. Hence, the point on an image plane

representingtheobjectvertexisapiercingpointontheimageplane.Astraightedge or line segment on an object is defined by two vertices. Therefore, theprojectionofthesetwoverticesonanimageplanedefinestheendpointsofthestraightedgeontheimageplane.

Connectingtheimagepointsbyalinedefinestheimagelinefortheobjectonthe image plane.When the shape on one image plane is completed, then theobservercanturnthrough90°(arotationalmovement)toviewtheobjectfromanotherprincipaldirection.InFigure2.6,sixviewdirectionsoffront,rear,top,bottom, right,and leftare indicated.Thisprocess is repeatedsoas togeneratethesixviewimagesontheimageplanes.Figure2.7showsthreeoftheimagesoftheobjectofFigure2.5.NotethedottedprojectionlinesinFigure2.7.Theyareshown to help in the visualization of the projection concept. If an object hascurvededgesorcontours,thentheedgesaredividedintotinylinesegmentsandthe projection described previously carried out. In this case, it is clear thatconstructingtheimageofacontourinanimageplanewillbeatedioustask.Thisshould help appreciate the availability of curve templates and instruments intraditionaldraftingandofspecialcurvesinCDDsystemssuchasBeziercurvesandnonuniformrationalbasicspline(NURBS).ABéziercurveisaparametriccurve frequently used in computer graphics and related fields for modelingsurfaces. NURBS is a parametric curve with precise mathematicalrepresentationsfor2Dor3Dobjectsthatcanbestandardshapes(suchasacone)or free-form shapes (such as a car body). It is frequently used in computergraphicsandCDD/CAM(computer-aidedmanufacturing)industrytocreateandrepresentcomplexobjects.InFigure2.7andFigure2.8, theintersectionoftwoprincipalplanesisanedgeknownasthefoldline.Linesofsightfromapointonaprincipalplanetoafoldlinemustbeatrightangle.

Figure2.6.Imageboxandobject.

2.7

2.7.1

Figure2.7.Objectviewsonprincipalplanes.

DRAWINGVIEWS

PRINCIPALVIEWS

Though an infinite number of view directions are theoretically possible, sixprincipalplanesareallthatareneededinorthographicprojection.Asmentionedearlier, the planar surfaces of the image box are called principal planes.Consequently,theimagescreatedontheseplanesarecalledprincipalviews.Thesix (6) principal views in orthographic projection are top, bottom, front, rear,left,andrightviews.Theviewsoftheimageboxcanbelaidoutonaflatsurfaceorpaperspace.Theseareobtainedbyconsideringthefold-lines(intersectionofimageplanes)intheimageboxtobeimaginaryhingesonwhichtheviewscanswing about. Therefore, for the image box, the faces can be opened up asdepictedinFigure2.8.WiththeobjectinsidetheimageboxinFigure2.7,thenFigure2.9iswhatisobtainedfortheprincipalviewsinpaperspace.

Figure2.8.Imageboxfacesandprincipalplanes.

2.7.2

Figure2.9.Layoutofsixprincipalviewsonflatpaper.

It is seen then that the 3Dobject ofFigure2.5 has nowbeen converted tomultiple 2D views in Figure 2.9 through the principles of orthographicprojection.Apartfromtheadvantageofsimplicityofthe2Dviews,thereistheabilitytoclearlyandcompletelydescribetheshapeandsizeofthe3Dobjectbymultiple2Dviews.

PROJECTIONSTANDARDS

Figure2.10a shows spatialquadrants1,2,3, and4as theyare conventionallyassumed. The horizontal and frontal principal planes are indicated in Figure2.10a.The third principal plane, called the profile plane is omitted for clarity.Figure 2.10b shows the planar representations of the spatial quadrants. In theprojectiontheory,anobjectcanbeassumedtobeinanyofthefourquadrants;however, the first and third quadrants are the preferred. In the first angleprojection(Figure2.11),theobjectisinfrontoftheprincipalplanesrelativetotheviewdirectionorpositionoftheobserver.Hence,theprojectedviewsoftheobjectareplacedbehindtheobject.

Figure2.10.Spatialandplanarquadrants.(a)Spatiallayout.(b)Planarlayout(Rightview).

Figure2.11.Firstangleprojection.

Figure2.12.Thirdangleprojection.

Forexample,thetopviewliesbelowtheobject,thefrontviewisbehindtheobject,andtherightviewistotheleftoftheobject.However,inthethirdangleprojection(Figure2.12),theprincipalplanesareinfrontoftheobjectrelativetotheviewdirection.Hence,theprojectedviewsoftheobjectareplacedbeforetheobject.Forexample,thetopviewliesontopoftheobject, thefrontviewisinfrontoftheobject,andtherightviewistotherightoftheobject.

The first angle projection is the standard in Europe, while the third angleprojection is the standard in the United States and Canada. The object viewsgenerated based on these two standardsmust be placed in the correct relativepositions.Standardsymbolsareused indrawings to indicate thefirstand thirdangle projections as shown in Figures 2.11 and 2.12, respectively. In either

2.7.3

2.7.4

standard,theobserver’spositiondefinestheviewdirectionandname.

STANDARDVIEWS

Though there are six principal views, three are chosen as standardviews.TheU.S.standardviewsaretop,front,andrightviewsandareshowninFigure2.13.Thesearebasedonthethirdangleprojectioninwhichtheobjectisassumedtobelocatedinthethirdquadrant.TheEuropeanstandardviewsarefront,top,andleft views and are shown in Figure 2.14. These are based on the first angleprojectioninwhichtheobjectisassumedtobelocatedinthefirstquadrant.Thefront viewmay be used as the reference view in both standards. In the U.S.standard,thetopviewislocatedontopofthefrontview,andtherightviewislocated to the right of the front view. This arrangement seems logical andintuitivelynatural.

IntheEuropeanstandard,thetopviewislocatedbelowthefrontview,whiletheleftviewislocatedtotherightofthefrontview.Thisarrangementappearscounterintuitive.Whenmore details about an object are desired, auxiliary andsectionviewsmaybecreated.Auxiliaryviewsareemployed to reveal the trueshape and size of features on inclined and oblique faces. Section views arecreatedtorevealhiddendetails.

PRINCIPALDIMENSIONSANDLAYOUT

Asmentioned earlier, a principal view reveals only two principal dimensions.Therefore, aminimumof twoprincipalviewsareusually required to showallthreeprincipaldimensionsofwidth(W),height(H),anddepth(D),asshowninFigure 2.15a. For example, the front view shows the width and heightdimensions, see Figure 2.15b. The depth dimension is not shown. Table 2.1summarizestheviewsandprincipaldimensions.

2.8

Figure2.13.U.S.standardviews.

Figure2.14.Europeanstandardviews.

Figure2.15.Principaldimensionsanddrawinglayout.(a)Objectprincipaldimensions.(b)Layoutofstandardviews.

Table2.1.Principalviewsanddimensions

Principalview Principaldimensions

Top,bottom Width,depth

Front,rear Width,height

Right,left Height,depth

NONUNIQUEVIEWS

An issue in orthographic projection is that projected views of different shapesmay look alike. Hence, some views are not necessarily unique. It takes aminimumof twoviews toestablish the shapeor formofanobject.Therefore,every effort must be made to avoid ambiguity in drawing representations by

2.9

generatingtheminimumviewsnecessarytouniquelydescribeanobject.Figure2.16showsexamplesofnonuniquesideviews.

REQUIREDVIEWSANDPLACEMENT

Adrawinginstandardorthoviewsrequiresthreeviews.Therequiredminimumnumber of views for describing an object depends on whether an object isregular or irregular. Regular objects have one or two lines of symmetry. Forexample, a sphere needs only one view for representation because of itssymmetryabout twoaxes.Componentsofuniform thickness (e.g., sheetmetalcomponents)may be described by one view. Such drawings normally includenotes specifying the object thickness. Objects with one line of symmetry andwithoutcomplicatedfeaturesmayberepresentedwithtwoviews.Examplesarecylindrical,conical,andpyramidalobjects.Irregularobjectsarewithoutlinesofsymmetry;theygenerallyneedtwoormoreviewsforrepresentation.Similarly,very complicated objects with inclined and oblique faces may need severalviews,includingauxiliaryandsectionviews.

Figure2.16.Nonuniquesideviews.

Viewsinmultiviewdrawingsshouldbeproperlyplacedonthelayout.Iftheviewsarecreatedwiththeaidofboundingblocksandmiterline,theviewswillbealignedaswillbeshown in thenext section. Ifviewsaregenerated fromasolid model (many CAD packages can do this), then proper placement andalignmentofviewsisaconcern.Besuretoplacethemcorrectlyaccordingtothedesired standard (U.S. or European standard). Figure 2.17 illustrates these

2.10

1.2.3.

points.IntheU.S.standard(thirdangleprojection),thetopviewisplacedontopofthefrontviewandtherightviewisplacedontherightofthefrontview.IntheE.U.standard(firstangleprojection),thetopviewisplacedbelowthefrontviewandthe leftviewisplacedon therightof thefrontview.OnlyFigure2.17a isacceptable because the views are correctly placed and aligned in third angleprojection,theothersarenotacceptable.

Figure2.17.Placementandalignmentofmultiviews.(a)Correctplacementandalignment.(b)Topviewnotaligned.(c)Frontviewnotaligned.(d)Rightviewnotaligned.

CONSTRUCTINGSTANDARDMULTIVIEWS

Standardorthoviewscanbeconstructedfromisometricsketchesanddrawingsorgenerated from solid models. The construction or generation process usesorthographic projection principles discussed in the previous sections. It isstrongly recommended that the student invests time and effort necessary forunderstanding the concepts and principles of an orthographic projection. Thetemptation of short-cuts should be avoided; short-cuts seem to produceprofessionalswhodonotunderstand thewhysofwhat theydo!Understandingconcepts and principles pay-off handsomely with time as the hard workingstudentsoondevelopshisorhershort-cutsfromthem.Thefollowingstepsmaybeusedtoconstructastandardmultiviewdrawing.

EnvisiontheimageboxasenlargementoftheB-box.Choosethefrontviewoftheobject.Constructthelayout.

4.5.6.7.8.9.10.

2.10.1

2.10.2

•••••

Drawvisiblefeatures.Drawhiddenfeatures.Addcenterlines.Checkandcorrecttheviews.Makecheckprint(s)andreviewthedrawing.Makefinalcorrections.Printorarchivedrawings.

Steps 1 to 10 are required for nondimensioned drawings. If drawings aredimensioned, for example, when preparing working drawings, dimensions,notes, and specifications are necessary, and Steps 7 and 8 are done afterannotation.

ENVISIONTHEBOUNDINGBOX

Mentallypicturetheboundingboxaroundtheobject.Enlargetheboundingboxtogettheimagebox.Thefacesoftheimageboxformtheprincipalplanesandbecome portions on the view layout. The bounding box helps to establish theprincipaldimensions for layoutconstruction.Figure2.18a isanobject that thestandardviewsarerequired,andFigure2.18bshowstheboundingboxisadded.

CHOOSEFRONTVIEW.

Choosing a correct front view is very important in multiview drawings. ThefrontviewfortheobjectinFigure2.18aischoseninFigure2.19a,andtheaxesandviewdirectionsareaddedinFigure2.19b.Thefollowingpointsshouldbeconsideredwhenmakingafrontviewchoice:

BestshapeormostdescriptiveprofileMostnaturalpositionofuseMoststablepositionShowsthelongestprincipaldimensionsContainstheleasthiddenfeatures

Figure2.18a.Object.

Figure2.18b.Boundingbox.

Figure2.19.Frontviewchoice,localaxes,andviewdirections.(a)Frontviewchoice.(b)Axesandviewdirections.

Oncethefrontviewischosen,theotherviewdirectionsarefixedandshouldbenoted.Itmaybehelpfultoimaginealocalorobjectaxesplacedonthelower-left corner of the B-box. The axes are laid out using the right-hand rule asindicatedinFigure2.19b.Thismakeseverypointontheobjecttohavepositivecoordinatevalues.Keepinmindthatthecoordinatesystemisalocalcoordinatesystem.That is,onecoordinatesystemisneededforeachobjectof interest.Aglobal coordinate systemwill have a fixed origin that applies to every object.The view directions must be correctly identified. The front view direction isparalleltotheY-axis,thetopviewdirectionpointsdownwardinthenegativeZ-axis,andtherightviewdirectionpointsleftwardalongthenegativeX-axis.

2.10.3

••

•

2.10.4

•

••

••

DRAWTHELAYOUT

Drawtheboundingblocksofthetopandfrontviews,seeFigure2.20a.Drawthemiterlineat45°beginningatthetop-rightcornerofthefrontviewboundingblock.Use projection lines to construct the right view bounding block, see Figure2.21b.

DRAWVISIBLEFEATURES(SEEFIGURE2.21A)

Chooseabaseview (top, front, right).The frontview is chosenas thebaseviewinFigure2.21a.Usevisualinspectiontoidentifyallvisiblefeatures.Draw edgesmoving from left to right by visual inspection. (Use the offsetbuttoninaCDDpackage).Drawedgesmovingfrombottomtotopbyvisualinspection.Drawvisibleshapefeaturesmovingfromlefttorightbyvisualinspection.

Figure2.20.Viewlayout.(a)Topandfrontviews’boundaries.(b)Boundingblocksforviews.

••

2.10.5

•

•

•••

2.10.6

2.11

Step1:

Figure2.21.Developmentofviews.(a)Visiblefeaturesdevelopment.(b)Hiddenfeaturesdevelopment.

Youdonotneedtocompleteeverythingonaviewtogoontothenextview.Decideonthenextview.

DRAWHIDDENFEATURES(SEEFIGURE2.21B)

Use projection lines and visual inspection to identify and locate hiddenfeatures.Usehidden line style forhidden featuresormovehidden features tohiddenlayer.Addhiddenfeaturestotheviews.Auxiliaryorsectionviewsmaybeneeded.Remember line style precedence.Object lines have precedence over hiddenlinesandcenterlines.Hiddenlineshaveprecedenceovercenterlines.Cutting-planelineshaveprecedenceovercenterlines.

ADDCENTERLINES

Placethecenterlineorcentermarkonallcirclesandarcs(seeFigure2.22).ThecompletedstandardmultiviewsdrawingoftheobjectinFigure2.18aareshowninFigure2.22.

GENERATINGVIEWSFROMSOLIDMODELS

Oneofthemajoradvantagesofsolidmodelingistheeasewithwhichdrawingviewscanbegeneratedonceasolidmodeliscreated.MostCDDpackagesmaketheprocessofgeneratingviewsveryfriendlyandtheprocesstakesasmalltimefractioncompared tomanualdrawing that the laterbecomes inefficient,costly,and very undesirable. While hidden lines are added to generated views,centerlinesareusuallynot.So,thedesigndrafterwouldhavetoaddcenterlinestotheviewsgenerated.Figure2.23andFigure2.24areillustrativeexamples.

Generatedrawingviews:Using the view placement routine, generate the drawing views for thecomponent from the solidmodel as shown inFigure2.23.Note that, in

Step2:

Figure2.23,hidden lineswereadded to theviewswhen theappropriateroutine isused,butcenterlinesaremissing.Ensure thatenoughspace isprovidedbetweenviewstomakeroomfordimensionswhenplacing theviews.Addcenterlines:

Figure2.22.Completedviews.

Figure2.23.Generatedviewsofacomponent.

Figure2.24.Plainmultiviewdrawing.

Centerlinesneedtobeadded.TheCADsoftwareusedherehasaroutine

1.

2.

3.4.

5.

6.

7.

8.9.

10.11.

12.

13.

14.

15.

for automatic centerline in addition to the views. After applying thisroutine,plaindrawingviewsareobtainedasshowninFigure2.23.

Thefollowingconstitutethemainprinciplesinanorthographicprojection:

Linesofsightareparallel inorthographicprojection,seeprojectionlinesinFigure2.20.Fold lines are the intersections of image planes and are placed midwaybetweenadjacentviews.Theyaregenerallyomittedforclarityinmultiviewdrawings,seeFigure2.20andcomparewithFigure2.9.Thereareonlysixpossibleimageplanes,seeFigure2.9.Every feature in one view must be aligned on a parallel projector in anadjacentview,seeFigure2.21.Distancesbetweenanytwopointsofafeatureinrelatedviewsmustbeequal,see center distance between holes in top and front views or top and rightviewsinFigure2.21.Featuresaretruelengthortruesizewhenthelinesofsightareperpendiculartothefeatureplanes,seecircleviewinFigure2.21a.Features are foreshortenedwhen the lines of sight are not perpendicular tothe feature planes, that is, features on inclined and or oblique faces areforeshortened.Parallelfeatureswillalwaysappearparallelinallviews.Surfaces that are parallel to the lines of sightwill appear as lines or edgeviews.Notwocontiguousareascanlieinthesameplane,seeFigure2.21a.The projection of an oblique line or oblique plane to the image plane isforeshortened.Anedgeviewlineinoneviewofamultiviewdrawingrepresentsafaceonthe3Dobject.Horizontal lines in front and top views have either visible or hidden linerepresentationsinsideview.Projection lines between views help in correctly locating features in theviewsandminimizeerrors.Theorthographicviewofacurveisdeterminedbyfirstdrawingtheshapeofthecurveinoneview.Then,dividetheshapeintosegmentswithasegmentbounded by two key points. Project the key points to the adjacent plane.Smallersegmentsgivemoreaccuraterepresentation.

2.12

•

•

••

••••

2.13

1.2.3.4.5.

6.

7.8.9.10.11.12.13.

14.15.16.17.18.

CHECKLISTFORMULTIVIEWDRAWINGS

All vertical lines in a top viewmust be projected to a front view or verseversa.Allfeaturesizelimitsinatopviewmustbeprojectedtoafrontvieworverseversa.Allhorizontallinesintopandfrontviewsmustbeprojectedtoarightview.Allfeaturesizelimitsintopandfrontviewsmustbeprojectedtoarightvieworverseversa.Allfeaturesmustberepresentedinallviews.Hiddenlinesmustbeproperlyrepresented.Centerlinesmustbeproperlyrepresented.Precedenceoflinesshouldbeapplied


Namethetwofundamentaltypesofprojection.Whatisthetypeofprojectioninanorthographicprojection?Whattypeofdrawingviewsarecreatedwithanorthographicprojection?Howaremultiviewsrelatedtoanorthographicprojection?Nametwootherprojection typesofparallelprojectionscommonlyusedforengineeringdesigngraphics.How many views can be created in orthographic projection based on thestandardviewdirections?WhichANSI/ASMEstandardprovidesguidelinesformultiviewdrawings?Howmanystandardviewsarerequired?WhatmultiviewstandardisadoptedinNorthAmerica?Howmanyprincipaldimensionscanberevealedinoneorthographicview?Nametheprincipaldimensionsthatareshownbytop,front,andrightviews.Listtheassumptionsmadeinanorthographicprojection.What is the minimum number of orthographic views for axial symmetricobjects?Whatisamiterline?Howisitusedinmultiviewdrawings?Defineprojectionlinesandimageplaneinanorthographicprojection.Whatfactorscanguideyouwhenchoosingafrontview?HowcanyourelatetheB-Boxtoanimageplane?Mustviewsinmultiviewsdrawingbeproperlyaligned?

19.

20.

2.14

Whenfeaturesareonsometypesoffaces,theyappearforeshortened.Whatarethesetypesoffaces?Howcanyoucorrectthedistortionsofforeshortenedviews?

CHAPTEREXERCISES

Createthestandardviews(top,front,andright)forthefollowingfiguresshownusingthethirdangleprojection.Chooseyourfrontviewandjustifyyourchoicewithalistofthreereasons.

FigureP2.1.Problem1.

3.1

3.2

CHAPTER3

AUXILIARYDRAWINGVIEWS

INTRODUCTION

An auxiliary view is an orthographic view that is created for a feature on aninclined or oblique face of an object. It is created from at least two principalviews with the aim of showing the true shape and size of the feature.Conceptually, it isanormalviewobtainedby lookingataplane inadirectionperpendicular to it because the direction of a plane is defined by an axisperpendicular to it. Though there is no limit to the number of auxiliary viewsthat can be generated from principal views, practical considerations restrictviews to preferred directions of inclined and oblique faces on objects.Consequently, a limited number of auxiliary views are normally needed intechnical graphics.A primary auxiliary view is the first auxiliary view that isobtained from twoprincipalviewsofanobject.Asecondaryauxiliaryview isgeneratedfromaprimaryauxiliaryviewandoneprincipalview.Third, fourth,andsoauxiliaryviewsmaybedrawn;however,mosttechnicalgraphicproblemscanbe solvedwithoneor twoauxiliaryviews.Successiveauxiliaryviewsareviewsobtained fromoneprincipal viewand a primary auxiliaryviewor fromtwootherauxiliaryviews.Usually,oneauxiliaryviewcansubstituteforoneofthestandardorprincipalviewsinamultiviewdrawing,andthusreducethetotalnumber of views necessary for complete description of a component. Hiddenlinesappearingbehindauxiliaryviewfeaturesareusuallynotshownforclaritypurposes.

UNDERSTANDINGAUXILIARYVIEWS

Auxiliary views are needed when a feature is foreshortened in one or moreprincipalviews.Featuresareforeshortenedwhentheyappearoninclinedandorobliquefaces.Foreshortenedimagesaredistorted,sothereisalwaysanecessitytoclarifysuchimagesintechnicalgraphics.Auxiliaryviewtechniquesallowusto look directly (perpendicularly) at a face on an object, and hence see thefeatures on it in true shape and size. Therefore the techniques of generatingauxiliary views help us correct the distortion of foreshortened images onprincipal views, though they are often tedious to create manually. However,auxiliaryviewscanbegeneratedeasilywithComputerDesignDrafting(CDD)packages.

In creating auxiliaryviews, someconceptsneed tobeproperlyunderstood.These include the true length (TL) line, edge view of a plane, inclined andobliqueplanes.ATLline isonewhosetruesize isrepresentedonaview.Theedge view of a plane is a line. This is the view of a plane when the viewdirectionisparalleltotheplane.Inclinedandobliqueplanescanberecognizedbyinspectingtwoadjacentprincipalviews.

Figure3.1a shows the case of an inclined facewhere the edgeview of thefaceisshowninoneprincipal(front)view.Thefaceisshownforeshortenedintheothertwoprincipalviews.InFigure3.1a,twoadjacentviewsaresufficienttoidentifythefaceasinclined(frontandrightorfrontandtop).Inaproblemwithan inclined face,onlyoneprimaryauxiliaryviewwill beneeded to create thetrue shape and size of a feature on it. Hence, for Figure 3.1a, an auxiliary isrequiredtorevealthetrueshapeoftheinclinedface.Figure3.1bshowsthecaseofanobliquefacewherenoedgeviewofthefaceisshowninaprincipalview.That is, theface isshownforeshortened in the threeprincipalviews. InFigure3.1b, a combinationof the front and topviewsor the front and right views isenoughtoidentifythefaceasobliquebecausetheplaneappearsforeshortenedineitherpair. In this case, bothprimary and secondary auxiliaryviewswouldbeneededtocreatethetrueshapeandsizeofthefeatureonsuchaface.

As the form of components gets more complicated, inclined and obliquefacesmaybecomepartofthefeatures.Tocreatethenecessaryauxiliaryviewforthetrueshapeandsizeoffacesandfeaturesonthem,firstidentifyorcreateanedgeviewoftheface; then,project thefaceinadirectionperpendicular totheedgeviewplane.Figure3.2ashowstwoadjacentviewsofalinewithendpoints1and2.Point1inthefrontviewisindicatedbyF1andH1inthetopview.Inthefrontview,thelineishorizontalandparalleltothefoldline,areferencelinebetween the two views.On the top (horizontal) view, the line is inclined andshows the true lengthof the line.Hence,aviewshowing the true lengthofaninclinedlineisadjacenttoaviewthatshowstheinclinedlineparalleltoafold

line.Foldlinesarenotalwaysshowninstandardorthographicview.Theymaybesafelyassumedtobemidwayinthegapbetweentheadjacentviews.Figure3.2bshowsanobliquefacewithnoTLline.TocreateaTLline,thelineF2-F4isdrawnhorizontal,paralleltothefoldline,andisprojectedtothetopviewasH2-H4.ThelineH2-H4istheTLlineoflineF2-F4.Theedgeviewoftheobliquefaceisdevelopedinaprimaryauxiliaryplanewithaviewdirectionparallel tolineH2-H4.TheprincipletotakenoteofisthattheedgeviewmustbecreatedwithaviewdirectionparalleltoaTLontheobliqueface.Inmanydrawings,TLlinecanbeidentifiedwheretwofacesonanobjectintersect.

Figure3.1.Inclinedandobliquefaces.(a)Inclinedface.(b)Obliqueface.

Inthecaseofaninclinedface,theTLlineistheedgeviewofthefaceitselfasinFigure3.2a.Hence,theprimaryauxiliaryviewderivedfromtheedgeviewgives the true shape and size for the face and the features on it. If a TL linecannotbeidentifiedonanobliqueface,onecanbecreatedasshowninFigure3.2b.OnceaTLlineisavailable,theedgeviewoftheobliquecanbecreatedina primary auxiliary viewwith the projection lines parallel to theTL line.Thetrueshapeandsizeoftheobliquefaceandthefeaturesonitcanthenbecreatedinasecondaryauxiliaryviewwiththeprojectionlinesperpendiculartotheedgeviewline.

3.3

3.3.1

3.3.2

Figure3.2.IdentifyingorcreatingaTLline.(a)Inclinedface.(b)Obliqueface.

VISUALIZINGAUXILIARYVIEWS

AUXILIARYVIEWIMAGEBOX

An image box can be constructed with an auxiliary plane included in theprincipalimagebox.Theauxiliaryplanemustbemadeparalleltotheinclinedorobliquefaceintheimagebox.Figure3.3aillustratesthisconceptforaninclinedface.ThelayoutoftheviewsintheimageboxisshowninFigure3.3b.Notethatthe right view is omitted in the layout. It is important to maintain the sameamount of distance for the nearest point on an image from all the fold lines(edgesoftheimagebox)inthelayout.Auxiliaryviewsmustbealignedwiththeauxiliary face in layout.Also,allprojection linesmustbeperpendicular to theauxiliaryplane.Theviewdirectionisalwaysparalleltotheprojectionlines.

FULLANDPARTIALAUXILIARYVIEWS

Auxiliaryviewsmaybecreatedasfullorpartialviews.Inafullauxiliaryview,all features in the view direction on the object are represented. This meansimagesofbothforeshortenedandnonforeshortenedfeaturesonprincipalviewsareshown.Inmanycases,theinclinedandobliquefacesareportionsofalargercomponent,withsomefeaturesappearingtrueshapeandsizeinsomestandardviews.Therefore,therealneedistorepresentonlytheforeshortenedfeaturesonauxiliary views. Hence, partial auxiliary views are most often needed tosupplement standardviews. Inapartialauxiliaryview,only the featuresonaninclinedorobliquefacearerepresentedontheauxiliaryview.Thisusuallyleadsto a clearer presentation, as additional noninclined or oblique features mightactuallyconfusetheview.

Figure3.3.Anauxiliaryimageboxandlayout.(a)Imagebox.(b)Layout.

Figure3.4.Typesofauxiliaryviews.(a)Full.(b)Partial.

For instance, consider Figure 3.4a that shows a full auxiliary view. It isobvious that the extra details in the auxiliary view of Figure 3.5a are betterrevealedintheprincipalviewsofFigure3.4awheretheyappearintruesizeandshape.Therefore,thepartialauxiliaryviewofFigure3.4bispreferred.Notethat,inthepartialauxiliaryviewofFigure3.4b,hiddenlineshavebeenomitted.Thisnormallyenhancesclarityofviewsascanbeverifiedbycomparing thepartialviewofFigure3.4bwiththeappropriateportioninthefullviewinFigure3.4a.Feature views appearing in true shape and size in principal views are notnecessaryinauxiliaryviews,theyjustcomplicatedrawings.

3.4

3.4.1

3.4.1.1

3.4.1.2

CONSTRUCTINGAUXILIARYVIEWS

Thissectiondiscussestechniquesforconstructingauxiliaryviewsforfeaturesoninclined faces and oblique faces. The true size and shape of features on aninclined plane need one auxiliary plane, a primary auxiliary plane fordevelopment.However, thetruesizeandshapeoffeaturesonanobliqueplanecan thedevelopedwithaminimumof twoauxiliaryplanes,namely,aprimaryauxiliaryplaneandasecondaryauxiliaryplane.

CONSTRUCTINGFEATURESONINCLINEDFACES

When a feature is on an inclined plane, the edge view of the plane will berevealedinoneof theprincipalviews.Thisviewshouldbechosenasthebaseview for developing the auxiliary view that will show the true shape of thefeature.As the auxiliaryview is created fromaprincipal view, it is a primaryauxiliary view. The steps to employ in constructing the auxiliary view areoutlinedasfollows.

Step1:CreateTwoPrincipalAdjacentViews

Create two adjacent principal or standard views. All the features on the twoviewsneednotbecompleted inorder toproceed to theauxiliaryview.Oneofthestandardviewsshouldshow theedgeview(line)of the inclined faceas inFigure 3.5. Identify this view as the base view (front view in Figure 3.5) forauxiliaryviewcreation.

Step2:DrawProjectionLinesforAuxiliaryView

Identitytheverticesofthefaceandusethemtodrawprojectionlines.InFigure3.6, theverticesof the face are the two endpoints of the inclined lineor edgeviewoftheface.Keypointsonfeaturesonthefacemaybeusedalsoindrawingprojection lines. The key points on the circular feature are the edges and thecenterlineofthehole.Drawprojectionlinesfromtheidentifiedverticesandkeypoints perpendicular to the face as shown in Figure 3.6. A fold line may bedrawn and used as a reference line for the transfer of dimensions betweenadjacentviews.Afoldlinemustbeparalleltotheedgeviewoftheinclinedfaceataconvenientdistance.AfoldlineisnotshowninFigure3.6.

3.4.1.3

3.4.1.4

Figure3.5.Twoprincipalviews.

Figure3.6.Projectionlinesforauxiliaryview.

Step3:DrawtheOutlineoftheInclinedFace

Establish the distance of each vertex on the auxiliary view from the adjacentprincipalview(rightviewinFigure3.6)tothebaseview.Transferthedistanceofeachvertex to theauxiliaryview,anddraw theoutlineof the inclined face.Figure3.7showstheconstructionoftheinclinedfaceoutline.

Step4:DrawtheFeatureontheInclinedFace

Establishthedistanceofkeypointsofthefeatureontheinclinedface(K2,K2,andK3intherightviewofFigure3.8)fromtheadjacentprincipalviewtothebaseview.Inthisexample,thesearetwohorizontalquadrantsontheellipseontherightviewandthecenterlineof thehole.Transfer thedistanceofeachkeypoint to the auxiliary view and draw the feature. Figure 3.8 shows theconstructionofthecirclefeatureontheauxiliaryview.Itisveryimportantthatthe principle of size transfer be properly understood: transfer size from thesecondviewpriortothecurrentauxiliaryview.

3.4.2

3.4.2.1

Figure3.7.Drawoutlineofface.

Figure3.8.Drawthefeature.

CONSTRUCTINGFEATURESONOBLIQUEFACES

Sometimes,afeaturemaylieonanobliqueface.Inthiscase,bothaprimaryandasecondaryauxiliaryviewwillbeneededtoestablishthetrueshapeandsizeofthefaceandthefeaturesonit.Theprimaryauxiliaryviewisusedtodeveloptheedgeviewof the face, and the secondary auxiliary view shows the true shapeandsizeofthefaceandfeature(s).Thestepstosolvethisproblemare:

Step1:CreateTwoPrincipalViews

InFigure3.9, twoadjacentprincipalor standardviewsarecreated.Again, thefullviewsneednotbecreatedinordertoconstructtheauxiliaryviews.Itmay,in

3.4.2.2

3.4.2.3

fact,benecessarytocriss-crossbetweentheprincipalandauxiliaryviewsduringthe development. Remember that none of these principal viewswill show theedgeviewof theoblique face.Some judgment isneeded inselectingelementsthat can reduce time and effort in the construction process. This comes withpracticeandexperience.

Step2:IdentifyaLineElementofTLontheObliqueFaceintheBaseView

If no line can be identified as of a TL on the oblique face on any view, thencreateahorizontallineontheobliquefaceinoneprincipalview,drawtheTLofthis line in the adjacent principal view; Figure3.2 givesmore information oncreatingaTLline.ChoosetheviewwiththeTLlineasabaseview.InFigure3.9,wecanidentifyaTLlineontheobliquefaceinthetopviewasindicatedinFigure3.10.This is the front edge between the top face and the oblique face.Hence,thebaseviewforauxiliaryviewscreationisthetopviewinFigure3.9.

Figure3.9.Principalviews.

Step3:DrawProjectionLinesforPrimaryAuxiliaryView

3.4.2.4

Identify the vertices of the oblique face and use them to draw the projectionlines. InFigure3.9, the vertices of the face are the endpoints of the base line(pointsK1andK2inFigure3.10)andthetoplineonthefrontendoftheobliqueface(pointsK3andK4inFigure3.10).ThekeypointsK5andK6areidentifiedfortheprojectionofobjectthickness.DrawprojectionlinesfromtheidentifiedverticesparalleltotheTLlineelement,seeFigure3.10.Notethatallprojectionlinesmustbeparalleltoeachother.

Figure3.10.TLlineandprojectionlines.

Step4:DrawtheEdgeView

Areferenceor fold linemaybedrawnandusedfor the transferofdimensionsbetween adjacent views.A fold linemust beperpendicular toprojection lines,seeFigure3.11.Oncethereferencelineisdrawn,theedgecanthenbecreatedby transferringdimensionsofkeypointsorvertices fromtwoviewsbehindasexplainedearlier.Itissufficienttodrawonlythelinesoftheedgeviewswithoutaddingthicknesssizes.InFigure3.11,thematerialthicknessesofthetwofaceshave been added. These dimensions could have been omitted without loss ofaccuracy.Thisview is theprimaryauxiliaryview that shows theedgeviewoftheobliqueface.

3.4.2.5

3.4.2.6

Figure3.11.Referencelineandedgeview.

Step5:DrawProjectionLinesforSecondaryAuxiliaryView

Fromtheverticesandkeypointsontheedgeview,drawprojectionlinesforthesecondary auxiliary view. These projection linesmust be perpendicular to theedgeviewline.ThisstepisshowninFigure3.12.

Step6:DrawtheOutlineoftheObliqueFace

EstablishthedistanceofeachvertexontheobliquefacefromthebaseviewinFigure3.9.Transfer thedistanceofeachvertexto theauxiliaryviewanddrawtheoutlineoftheobliquefaceasshowninFigure3.13.

3.4.2.7

Figure3.12.Projectionfromedgeview.

Figure3.13.Drawoutlineofanobliqueface.

Step7:DrawtheFeature(s)onanObliqueFace

Establish thedistanceofeachkeypointonfeature(s)on theobliquefacefromthe baseview in Figure 3.9. Transfer the distance of each key point to thesecondaryauxiliaryviewanddrawthefeature(s)asshowninFigure3.14.

3.5

Figure3.14.Drawfeature(s)onanobliqueface.

GENERATINGAUXILIARYVIEWSFROMSOLIDMODELS

Creating auxiliary views is less cumbersome with solid models using CDDpackages. The shapes of inclined and oblique faces and the features on thempresent little difficulty with solid models. Most modern CDD packages withsolidmodeling capability include routines that can be used to create auxiliaryviewseasilyfromsolidmodels.ThedetailsintheprocessofcreatingauxiliaryviewsvarywitheachCDDproduct.Inmostcases,creatinganauxiliaryviewforan inclined face is aone-or two-stepprocess,whilecreatinganauxiliaryviewfor an oblique face is a two- or three-step process after the base views arecreatedoridentified.

Theconceptofplanesandfacesshouldbeproperlyunderstoodwhendealingwith solids.A plane is a flat surface of infinite length andwidth.A face is asurfaceonanobjectandmaybeflatorcurved.Acylindrical faceonapipe iscurvedsurface,forexample.Aflatfaceisaportionofanimaginaryflatplane.AuxiliaryviewsaregeneratedfromflatplanesbyCDDpackages.Theusermustspecify a plane when creating an auxiliary view. CDD software creates fullauxiliaryandpartialviewsdependingonthelengthofthecuttingplanedefined.Some dressing of the auxiliary view may be needed. The view direction isassumed to be perpendicular to the plane that is selectedwhen generating theauxiliaryview.

3.5.1

3.5.1.1

3.5.1.2

GENERATINGAUXILIARYVIEWSFORANINCLINEDFACE

As an illustration, we will revisit Figure 3.5 in discussing the technique forgeneratinganauxiliaryviewforaninclinedface.Careisneededwhenselectingtheauxiliaryplane; itmustbeperpendicular to theviewdirection.SolidEdgepackagewasusedinthisexample.

Step1:CreateTwoStandardViews

First, generate twoadjacentprincipal views from the solidmodel as shown inFigure3.15.Identifythebaseviewastheprincipalviewshowingtheedgeviewoftheface.Inthisexample,thefrontviewisthebaseview,whiletheleftviewistheadjacentprincipalview.

Figure3.15.Principalviews.

Figure3.16.Fullauxiliaryview.

Step2:SelecttheAuxiliaryViewButton

In someCDD packages, a commandmight be needed to invoke the auxiliaryviewroutine.Inmanycases,abuttonisavailableinthepaperspaceenvironment

3.5.1.3

3.5.2

3.5.2.1

3.5.2.2

that can be selected to invoke the auxiliary view routine.Once this routine isactive,itwillrequesttheusertoselecttheplaneforthedesiredauxiliaryview.InFigure3.16,theplaneofinterestisindicated.Thelinesegmentofthefacewasselectedasalinefeatureontheplane.

Step3:PlacetheAuxiliaryView

Withtheplaneselected,theroutinerequeststheusertoselectapositionfortheauxiliaryview.Drag thecursor to a convenientpositionandclick toplace theview.InFigure3.16, theviewdirection is indicated,but thiswasgeneratedbythe software. The full auxiliary view created by the software is shown. Theinclinedfacewillshowon theview.Likewise,all thefeatureson thefacewillshow.

GENERATINGAUXILIARYVIEWSFORANOBLIQUEFACE

As an illustration, we will revisit Figure 3.9 in discussing the technique forgeneratinganauxiliaryviewforanobliqueface.

Step1:CreateTwoStandardViews

Asintheinclinedfaceproblem,generatetwoadjacentprincipalviewsfromthesolidmodelasshowninFigure3.17.IdentifythebaseviewastheprincipalviewshowingaTLelement.IfnoTLelementisfoundonaprincipalview,onemustbecreated.Inthisexample,thetopviewisthebaseview,whilethefrontviewistheadjacentprincipalview.

Step2:DefinePrimaryAuxiliaryPlane

Once a TL is identified, see Figure 3.18, the primary auxiliary plane can bedefined. This planemust be perpendicular to the TL element. If no such lineexistson thebaseview, thenonemustbecreated. InFigure3.18, theprimaryauxiliaryplaneisindicatedinthetop(base)view.

3.5.2.3

Figure3.17.Standardview.

Figure3.18.Edgeviewfrombaseview.

Step3:CreatethePrimaryAuxiliaryView.

Invoke the auxiliary view routine either with a command or by selecting abutton. The routine will request the user to select the plane for the desired

3.5.2.4

3.5.2.5

auxiliary view, so select the plane accordingly. With the plane selected, theroutine requests the user to select a position for the auxiliary view. Drag thecursor toaconvenientpositionandclick toplace theviewasshowninFigure3.18.Afullauxiliaryedgeviewshouldbecreatedbythesoftware.

Step4:DefinetheSecondaryAuxiliaryPlane.

WiththeedgeviewlineasaTLelement,usethesameprocedureasexplainedinStep2todefinethesecondaryauxiliaryplane.Figure3.19illustratesthisstep.

Step5:CreatetheSecondaryAuxiliaryView.

Invoke the auxiliary view routine either with a command or by selecting abutton. Then, select the secondary auxiliary plane. Next, place the view inposition by dragging the cursor to a convenient position and click. A fullsecondaryauxiliaryviewshouldbecreatedbythesoftwareasshowninFigure3.19.Theobliquefacewillshowontheview.Likewise,all thefeaturesontheface will show. As can be noticed, centerlines and center marks are notautomatically added to auxiliary views generated from solid models by somepackages.Thesemustbe addedasdesired in standarddraftingpractice.Thesefeatureswereaddedinthetwoexamples(Figure3.16andFigure3.19).

Figure3.19.Fullauxiliaryviewforanobliqueface.

3.6

3.7

1.2.3.4.5.6.

COMBINEDSTANDARDANDPARTIALAUXILIARYVIEWS

Whenconstructingviewsforadrawing,timeandeffortcanbesavedbyuseofpartialauxiliaryandstandardviews.Forexample,considerFigure3.20inwhichtwostandardviews(topandright)areshownaspartialviews.Also,theauxiliaryviewisshownasapartialview.Thus,threepartialorthographicviewsandonefull standard (front) view can adequately convey the necessary shape anddimensionalinformationaboutthecomponent.Ifasolidmodelisnotavailable,sothattheviewsaredrawnfromasketchorisometricdrawing,alotoftimeandeffortwill be saveddrawing thepartialviews insteadof the full views for thefour necessary views. The isometric insert is added in Figure 3.20 to aidvisualization.Theuseofpartialviewsshouldbekeptinmindbydesigndrafters,asproductivityisanimportantconcernforsupervisorsandemployers.Ifviewsaregeneratedfromsolidmodels,thestandardviewsobtainedwillalwaysbefullviews. These standard viewsmay be converted to partial views bymodifyingthenmanually.However, someCDDpackagesallowpartial auxiliaryviews tobecreatedfromsolidmodelsbydefininganedgeviewlengththatspansonlytheportionofinterest.

Figure3.20.Partialauxiliaryandstandardviews.


Whatisanauxiliaryview?Whyareauxiliaryviewssometimesnecessary?Defineinclineplaneandobliqueplanes.Whatistheminimumauxiliaryview(s)foranobjectwithaninclinedface?Whatistheminimumauxiliaryview(s)foranobjectwithanobliqueface?Definethefollowing:

(a)(b)(c)(d)

7.8.

3.8

TLofaline.Edgeviewofaplane.Primaryauxiliaryview.Successiveauxiliaryview.

Whatarefullandpartialauxiliaryviews?Whenisapartialauxiliaryviewhelpful?

CHAPTEREXERCISES

Create standard and auxiliary views for each of the following figures.All thefigures, except the last, will need at least one auxiliary view. The last figureneedsmorethanoneauxiliaryview.


4.1

4.2

CHAPTER4

SECTIONDRAWINGVIEWS

INTRODUCTION

A section view is an orthographic projection view drawn to reveal internal orhidden features in an object. Section views are used to supplement standardorthographic view drawings in order to completely describe an object. Theyimprovevisualizationofdesigns,clarifymultiviews,andfacilitatedimensioningofdrawings.Hence,theyareanimportantaspectofdesignanddocumentation.Sectionviewsare createdbydefiningan imaginarycuttingplaneorplanesonthe object, so that the observer can see the internal details. Hidden lines aregenerallynotshowninsections.Hatchlines(alsocalledsectionlines)areusedto indicate solid materials that are cut through. A hatch pattern has certainattributes, such as orientation and line spacing, which are used to representspecificmaterialsorgroupofmaterials.Bothpartandassemblysectionscanbecreated.Sometimes,auxiliarysectionviewsmaybeneededforclarity.

CONCEPTOFSECTIONS

Inanorthographicprojection,thestandardprojectionplanesaretop(horizontal),front (frontal), and side (profile). The frontal and profile planes are vertical,whilethetopishorizontal.Standarddrawingviewsarecreatedontheseplaneswith preferred view directions. The view direction for the frontal and profileplanesishorizontal,whiletheviewdirectionforthehorizontalplaneisvertical.Figure4.1a shows the standard front and top views of a cylinder. Figure4.1bshowsthesamecylinderinmixed(standard,section,cutisometric)views,withthefrontviewconvertedtoasectionview.Severalelementsassociatedwiththe

conceptofsectionsareindicatedinFigure4.1b.Theseare(i)cuttingplaneline,(ii)viewdirection,(iii)removedportion,(iv)retainedportion,(v)hatching,and(vi)sectioncaptionorlabel.

Figure4.1.Conceptofsections.(a)Standardviews.(b)Mixedviews.

The cuttingplane is an imaginaryplane that passes through theobject at aposition of interest. It is represented by a line (the edge view of the sectionplane)inanadjacentviewtothesectionview.InFigure4.1b,thecuttingplaneisverticalbecauseitsedgeviewisseenonthehorizontalplane.Cuttingplanescanchangedirectionwithinanobject.Theviewdirectionisthelineofsightorthedirectionan imaginaryviewer is facing.Theviewdirection is indicatedby thearrowhead and is perpendicular to the cuttingplane. InFigure4.1b, theviewdirection is horizontal.The removedportion is theportionof anobject that isassumedtohavebeenremovedinorder toexpose the interior. It is thecut-outportionoftheobject.Theviewerisabletodirectlyseetheinterioroftheobjectwhenthecut-outisremoved.

Theretainedportionis theportionofanobject that isassumedtobeleft infront of theviewer.Thehatching is thepatternof hatch lines used to indicatesolidmaterial.Thesectionlabelisthenamegiventothesectionorcuttingplane.A very important difference between standard and section views is thereplacementofhiddenlinesinstandardviewswithvisiblelinesinsectionviews.Thisisveryfundamentalsinceitindicatesthefeatureisnowvisibleinasectionview.ComparingthestandardandmixedviewsofFigure4.1shows theclarityadvantage of section views. Another advantage of section views is that thevisiblelinesfromhiddenlinesinstandardviewscanbeusedfordimensioning;hidden lines are not used for dimensioning. When parts or assemblies havecomplex internal features, hidden lines in standard views become confusing,sectionsarethenindispensable.

4.3

4.4

CUTTINGPLANELINESTYLES

Acuttingplaneisrepresentedbyalinethatshowstheedgeviewofthecuttingplane.A limited number of line styles are used to represent cutting planes. InFigure4.2, the common line styles for cutting planes are shown.They are (a)thick centerline, (b) thick phantom line, and (c) broken visible line. Therepresentationin(c)isusedifthecuttingplanelinewouldhideimportantdetailsinadrawing.Eachoftheselinesisusuallyjoinedtoanarrowateachend.Thedirectionofthearrowistheviewer’slineofsight.Cuttingplanelinesaredrawnintheviewadjacenttothesectionviewandmaygobeyondtheboundaryoftheadjacentview.Thethicknessofacuttingplanelineshouldbemorethanthatofnormalvisibleline.

Figure4.2.Cuttingplanelinestyles.(a)Thickcenterline.(b)Thickphantomline.(c)Brokenvisibleline.

HATCHPATTERNS

Hatch lines are thin lines, andwhen they are laid out in a specific angle andspacing, a hatch pattern is formed. A hatch pattern is always within a closedboundary.Ifthereisagapinasection,hatchingwillnotoccurwhenusingCDDsystems. Spacing of hatch lines should enhance readability.Depending on thesizeofthedrawing,itmaybebetween1.5mm(0.06in)and6mm(0.25in)inrelatively small drawings. Likewise, the inclination of hatch lines should beguided by clarity. The angle of inclination for hatch lines normally variesbetween15°and75°.Popularanglesare15°,30°,45°,60°,and75°.Theangle45°isthedefaultangleinmostCDDsoftware.Hatchlinesmustnotbedrawnorplaced parallel to object lines or features in a section. In Figure 4.3, the leftcolumn views have hatch lines parallel to some object features, and they are,therefore, unacceptable. The acceptable representations are shown in the rightcolumnviews.Theangleofinclinationofthehatchlinesmustbedifferentfromthe angles of inclination of all the features forming the boundary of a hatchpattern. Figure 4.4 shows some examples of assembly hatch patterns. Whencomponentsareassembled,thehatchpatternsmustnotbeparalleltoobjectlinesorfeaturesofhatchboundary.Also,hatchlinesareinclinedatdifferentanglesin

eachcomponentinordertodistinguishthem.

Figure4.3.Hatchpatternlayout.

Figure4.4.Assemblyhatchpatterns.

4.5

Figure4.5.(a)Materialtypehatchpatterns.(b)Materialtypehatchpatterns.

Conventionally, some hatch patterns are associated with specific materialsand Figure 4.5 shows some material hatch pattern types. However, theproliferationofavailablematerialstodaymakesit impractical tohaveauniquehatch pattern for material types and grades. Thus, selected material hatchpatterns are in common use. In architectural drawings, some material hatchpatternsare inpopularuse.Machinedrawingsusefewmaterialhatchpatterns,andANSI31patternforcastironinFigure4.5istherecommendedpatternformachine drawings. This pattern may be used for all types of materials inmachinedrawings.

SECTIONVIEWREPRESENTATIONANDPLACEMENT

Properrepresentationofsectionfeaturesisveryimportant.Everyfeaturedirectlyexposedtotheviewerneedstobeincludedasvisibleentitiesinthesectionview.Gapsbetweenfeaturesegmentsmustnotbeallowed.InFigure4.6,twosectionview representations aregiven.The left representation is right,while the rightrepresentation iswrong because of gaps between the view segments. The linefeatures omitted in the right representation are clearly visible in the indicatedsectionplane.

The section viewposition in a drawing has a definite relationshipwith theviewdirection.Asectionviewshouldbeplacedbehindthetailendoftheviewdirectionarrow.Figure4.7illustratestheapplicationofthisprinciplefor(a)topsection view, (b) front section view, and (c) right section view. Sufficient gapshouldbeallowedbetweenthesectionandtheadjacentviewitisderivedfrom.Thisgapisveryimportantbecausesufficientspacemustbemadeavailablefordimensionplacement.

4.6

4.6.1

4.6.2

Figure4.6.Sectionviewrepresentation.(a)Right.(b)Wrong.

Figure4.7.Placementofsectionviews.(a)Topsectionview.(b)Frontsectionview.(c)Rightsectionview.

SECTIONVIEWTYPES

Sectionviewsmaybeclassifiedindifferentways.Forourdiscussions,weshallgroupthemintofull,partial,andspecialsectionviews.Infullsectionviews,thefulllengthoftheprincipaldimensionperpendiculartotheviewdirectionoftheobject is shown in a section view. Hence, the cutting plane or planes passthroughthewholecross-sectionoftheobject.Partialsectionviewsdonotrevealthewhole sections,but showaportionof the interior.Special sections includeauxiliarysections,assemblysections,andun-sectionedfeatures.

FULLSECTIONVIEWS

Full section views provide section views along the full length of the cross-sectionofanobjectandincludestraight,offset,removed,revolved,andalignedsectionviews.

STRAIGHTSECTIONS

4.6.3

Astraightsectionisalsocalledafullsectionbysomeauthors.Thecuttingplaneforastraightsectionscutsrightthroughthemiddleoftheobject,sothatonehalfof it is revealed after the second half is imagined removed. Thus, a straightsection is created from a single cutting plane. Straight sections are best forobjects with an axis of symmetry. Inmultiview drawings, a section view canreplace a standard view, and straight sections are commonly, thus, employed.Figure4.8showsanexampleofastraightsectionview.

OFFSETSECTIONS

Offset sections are similar to straight sections, except that the cutting planechanges direction at 90° at a time as it goes through the entire object. Offsetsections have two ormore parallel cutting planes. They are used for complexpart with a number of important features that do not lie on the same plane.Figure 4.9 is an example of an offset section view with three cutting planesoffsetfromoneanother.Notethat,inthesectionview,theoffsetcuttingplanesappearcollinear.Multipleoffsetsectionsarepossibleinirregularobjects.

Figure4.8.Straightsectionview.

4.6.4

4.6.5

Figure4.9.Offsetsectionview.

REMOVEDSECTIONS

Removedsectionsarefullsectionviewsplacedataconvenientpositionfromtheadjacentview,butlinkedwiththecuttingplaneeitherbyalineorviewlabelasshowninFigure4.10.Theyaredisplacedfromthenormalviewpositionanddonotneedtobeofthesamescaleastheadjacentviewtheyarederivedfrom.Ifthescalefortheremovedviewisdifferentfromtheadjacentview,itshouldbeindicated as a local note. It is convenient to display different removed sectionviews along the length of an object if it has varying cross-sections in thatdirection;seeFigure4.10.

REVOLVEDSECTIONS

Arevolvedsectionissimilartoaremovedsection,exceptthatthesectionviewissuperimposedonthecuttingplaneafter thesectionhasbeenrotatedthrough90°. The axis of revolution is indicated with a centerline as shown in Figure4.11. This representation is attractive when space constraint is an issue. Thesectionviewscale is the sameas the standardview.The sectionviewscanbeplaced with or without breaking the visible lines adjacent to them on thestandard view. Feature lines from the standard viewwithin the revolved viewshouldberemovedcompletely.Revolvedsectionviewsshouldbedrawnasseenfrom the view direction. Sections of bars, lever arms, spokes, and otherelongatedobjectsarecommonlyrepresentedinrevolvedsectionview.

4.6.6

4.6.7

Figure4.10.Removedsectionviews.

Figure4.11.Revolvedsectionviews.

ALIGNEDSECTIONS

In aligned sections, the cutting planes are not parallel, but inclined at someangle.Thelineof intersectionisusuallyat thecenterof theobject.Likeoffsetsections, the cutting planes are made to pass through features of interest asshown inFigure4.12. In the section view representation, one of the planes isrotated through some angle to align it with the other, as indicated in Figure4.12a.Thefeatureisthenprojectedonthealignedplane.Thisforcedalignmentmakes the section view looks pleasing and easier to visualize. Practicalconsiderationsorconventionalrules,thus,overridestrictprojectionprinciplesinalignedsectionviews.

Figure4.12.Alignedsectionviews.(a)Componentwitharms.(b)Componentwithoutarms.

PARTIALSECTIONVIEWS

4.6.8

4.6.9

Partialsectionviewsprovidesectionviewsofaportionofanobjectandincludehalf,broken,anddetailsectionviews.

HALFSECTIONVIEWS

Halfsectionshave twocuttingplanes thatareat90°,allowingaquarterof theobjecttobeimaginedremoved.Acenterlineisusedtodemarcatethesectionedportion from the un-sectioned portion in the section view as shown in Figure4.13.Sometimes,hiddenlinesareshownontheunsectionedpart.Halfsectionsarebestforobjectswithtwoaxesofsymmetry.

BROKENSECTIONVIEWS

Abroken section is a sectionexposedbya cutoutof aportionof anobject asshowninFigure4.14.Abrake line is used to show theboundarybetween thesectionedandun-sectionedportionofthedrawing.Acuttingplaneisnotshowninabrokensection.Abrokensection isused to limit theareaof interest inanobject.Itsavestimeandcouldsubstituteforfullorhalfsection.

Figure4.13.Halfsection.

4.6.10

4.6.11

4.6.12

Figure4.14.Brokensection.

DETAILSECTIONVIEWS

A detail section view is similar to a broken section view, except that it ispositionedoutsidethestandardview.Also,itisusuallyofenlargedscalesoastoreveal greater detail around the area of interest in the object.This givesmoreclarity,anditisofteneasiertoplacedimensionsondetailsectionviews.Figure4.15showsadetailviewofakeyway.

SPECIALSECTIONVIEWS

Sectionviewsderived fromnonprincipalviews suchasauxiliary sectionsmaybe considered as special section views, as they are obtained by applyingsectioning rules. Similarly, special application section views such as assemblysectionsandfeaturesorparts thatarenotsectioned indrawingsbyconventionarespecialsectionviews.

AUXILIARYSECTIONS

Auxiliary views (full or partial) may be sectioned, and standard conventionsapply to them.Forexample, the sectionviewshouldbeplacedon the tail endsideoftheviewdirectionarrow,andthereshouldbeavisiblegapbetweenthe

4.6.13

sectionviewandadjacentstandardview.Ahatchpatternshouldbeplacedwithcarebecausetheauxiliaryviewisinclinedinposition,andhatchlinesmustnotbe parallel to boundary line features. Figure 4.16 shows an example of anauxiliarysectionview.

Figure4.15.Detailsectionview.

Figure4.16.Auxiliarysectionview.

ASSEMBLYSECTIONS

Assembly sections are sectionviewswithmore thanonecomponent shown in

4.6.14

their relative fitted positions. They are very useful in checking clashes orinterferences of adjacent components in a unit. Adjacent components in anassembly section are hatched at different angles to clarify a drawing.Componentsareusuallynumberedandabillofmaterials(BOM)orpartslistisattachedtothedrawing.Figure4.17isanexampleofanassembly(full)sectionview, but without a parts list. Assembly sections may be full or half sectionorthographicorpictorialviewsoftheunitorproduct.

UN-SECTIONEDFEATURES

Somefeaturesarenothatchedinsectionviewsifthecuttingplaneisparalleltotheir axes. Such features are normally thin and include ribs, webs, lugs, andspokes.However,ifthecuttingplaneisperpendiculartotheiraxes,theymaybehatched.Figure4.18showsthecuttingplanesareparalleltoalugandspokes.Inasectionview, thesefeaturesareun-hatchedbecauseof thisparallelgeometricrelationship.InFigure4.19,thecuttingplanesareparalleltoaribandwebintheA-A section views, and the rib and wed are un-hatched or un-sectioned. ThecuttingplanesfortheB-Bsectionsaredefinedperpendiculartotheribandweb.In this case, the rib and web are hatched or sectioned because of theperpendiculargeometric relationship.Figure4.20 shows a shaft, key, bolt, andnut in section.By convention, these components are not hatched as indicated.Someotherstandardpartsorcomponentsnothatched insectionviews includepins,dowels,fasteners,gears,bearings,andsprings.

Figure4.17.Assemblysectionview.

4.7

Figure4.18.Un-sectionedfeatures.

Figure4.19.Hatchingun-sectionedfeatures.

Figure4.20.Un-sectionedparts.

CONVENTIONALBREAKS

Whenobjectsarelongandofconstantcross-section,theirlengthmaybereducedwithbreaklines.Breaklinesareeffectiveinsavingtimeandspace.Theyallowthe scale of a drawing to be increased. Figure 4.21 shows examples of

4.8

4.8.1

Step1:

conventionalbreaklines.

Figure4.21.Breaklinesfordifferentshapesandmaterials.

CONSTRUCTINGSECTIONVIEWS

In the following discussion, two illustrative examples for constructing sectionviews are considered. This is because, creating the different types of sectionview with constructional techniques follow the same basic procedure. Thisprocedure has the following steps: Step 1: Create standard view(s); Step 2:Createsectionplaneline(s)andfeatures;andStep3:Hatchsectionandfinishthedrawing.

CONSTRUCTINGASTRAIGHTSECTION

Figure 4.22 shows the three-step procedure applied in the construction of astraightsectionview.

Createastandardview.Using the techniques discussed in Chapter 2 for standard orthographic

Step2:

Step3:

4.8.2

Step1:

view creation, create one or two standard views as necessary. Aftercreating thenecessary standardviews, theoutlineof the sectionview isthen created as shown in Step 1 of Figure 4.22. Centerlines may beomittedatthisstage,butitisrecommendedthattheyshouldbeincluded.Createsectionplanelineandfeatures.Choose a sectionplane line style anduse it to define the sectionplane.Using projection lines as shown in Step 2 of Figure 4.22, project thefeatures on the section plane from the top view to the section view.Rememberthathiddenlineschangetovisiblelinesinsectionview.Hatchsectionandfinishdrawing.Apply the hatch lines to the section and make sure they are properlyinclined. Then, check and ensure that centerlines are placed correctly.Checkandcorrectanyerror.Addasectionlabel.

CONSTRUCTINGANALIGNEDSECTION

Figure 4.23 shows the three-step procedure applied in the construction of analignedsectionview.

Createstandardview.Create standard views as necessary. The section view outline is thencreatedasshowninStep1ofFigure4.23.

Figure4.22.Constructingaregularsection.

Step2:

Step3:

4.9

Step1:

Step2:

Figure4.23.Constructinganalignedsection.

Createsectionplanelineandfeatures.Using projection lines as shown in Step 2 of Figure 4.23, project keypointsonthefeaturesofthelowerrightarmtotheverticalcenterline.Thebaseoftheslotandthetipofthearmarethenecessarykeypointsinthiscase.Then, transfer theprojectedpoints to thecentervertical line to thesection view. Remember that hidden lines change to visible lines insectionview.Hatchsectionandfinishdrawing.Apply the hatch lines to the section and make sure they are properlyinclined. Then, check and ensure that centerlines are placed correctly.Checkandcorrectanyerror.Addasectionlabel.

GENERATINGSECTIONVIEWSFROMSOLIDS

Creating sectionviews fromsolidmodels isquite straightforward.The routineforcreating sectionsassumes that theuserhasa standardviewonscreen.Thenextstep is tocreate thecuttingplane line,and this ismostoftenastepof itsown.Then, theusermaybeprompted toplace theviewormay terminate thestep for the cutting plane and activate another button or initiate anothercommand to place the view. Centerlines are most often added to view on aseparate step, and the inclination of the hatch linesmay have to be adjusted.Figure 4.24 shows the three-step procedure applied in the generation of analignedsectionview.

Createastandardview.Create standard views as necessary, as shown in Step 1 of Figure 4.23usingtheroutinefororthographicviewgeneration.Createsectionplaneline.Using the CDD routine for the cutting plane line creation, define thecutting plane as shown in Step 2 of Figure 4.24. Some CDD packagegives the direct projection for aligned section. This must be manuallycorrectedtoconformtoconventionsinsectionviews.

Step3:

4.10

1.2.3.4.5.6.

7.8.9.10.11.12.13.14.15.

4.11

Figure4.24.Generatingasectionfromsolidmodel(SectionA-A).

Hatchsectionandfinishdrawing.Check the hatch lines of the section and make sure they are properlyinclined.The inclinationmayhave tobeadjusted forsatisfactory result.Then, check and ensure that centerlines and section label are placedcorrectly.Checkandcorrectanyerror.


Whatisasectionview?Whataretheadvantagesofsectionviews?Whatisacuttingplane?Arehiddenlinesnormallyshowninsectionviews?Whatistheimportanceoftheviewingdirectioninsectionviews?What isahatchpattern?Howdoyoudifferentiatehatchpatterns insectionviews?Sketchthehatchpatternforcastironandconcrete.Listthecommontypesofsectionviewsdiscussedinthechapter.Howisaremovedsectionviewdifferentfromarevolvedsectionview?Howisanalignedsectionviewdifferentfromarevolvedsectionview?Howisabrokensectionviewdifferentfromadetailsectionview?Howisastraightsectionviewdifferentfromanoffsetsectionview?Whatistheadvantageofhalfsectionviewoverstraightsectionview?Listthreetypesofobjectsthathatchingmaynotbeappliedinsectionview.Wherewouldyouconsideranauxiliarysectionview?

CHAPTEREXERCISES

Createstandardandsectionviewsforthefollowingfigures.Ensurethatthetypeofsectionviewchosenisappropriateforeachfigure.

5.1

CHAPTER5

BASICDIMENSIONING

INTRODUCTION

Dimensioning refers to the addition of size values to drawing entities.Dimensions are required for points, lines, arcs, circles, and so on, which arerelatedfunctionallyorcontrolrelationshipofotherfeatures.Basicdimensioningistheadditionoffunctionalordesignandnominalsizestofeaturesondrawingviews.Thisisprobablygoodonlyforsketchesandpreliminarydesigndrawingsbecause tolerances are additionally required in working drawings.Most CDDsoftwarecanautomaticallyaddbasicdimensionstoadrawing.But,somefine-tuningwouldnormallybenecessarytoachieveacceptableresults.ANSI/ASMEY14.5MisthestandardfordimensioningpracticeintheUnitedStates.Studentsshould familiarize themselves with this standard; even though the mainguidelines are incorporated in the discussions that follow from a practicalperspective.

Atechnicaldrawingconsistsofimagesandannotationsofanobjectarrangedin a prescribed order.Wemay distinguish between engineering diagrams anddrawings. Engineering diagrams have views that may be a combination ofpictorialview,standardorthographicviews,auxiliaryviews,andsectionviewswith hidden lines and centerlines, butwithout orwith incomplete dimensions.Engineeringdrawingsareobtainedbyaddingdimensions,tolerances,andnotesto engineering diagrams.Engineering diagrams are normally createdmanuallybefore dimensions are added to them in traditional drafting. In CDDenvironments, they can be constructed or generated from 3D models. Ifgeneratedfrom3Dmodels,hiddenlineswillbeshownbymostCDDpackages,butsomemaynotshowcenterlines.Theuserthenwouldhavetoaddcenterlinesandhidden lines ifnotalreadyadded to thegeneratedviews inorder tocreate

5.2

•••••

5.2.1

•

•

engineeringdiagrams.Fortunately,routinesorcommandsarenormallyavailableintheseCDDpackagesforaddingcenterlinesorhiddenlinesautomaticallyinaseparatestep.

ENGINEERINGDRAWINGANDSIZEDESCRIPTIONS

Anengineeringdrawingisaprecisetechnicalgraphicmodelthatcommunicatesdesign intent. It is usedbymanufacturers tomakeaproduct and inspectors todetermine whether the product should be accepted. An engineering drawingshouldconveythefollowinginformation:

Shapeorgeometriccharacteristicsofcomponent(drawingviews).Overallsizeofcomponentanditsfeatures.Tolerancesonsizes.Materialforthecomponent.Specificationsornotesforrequirementssuchasheattreatment,surfacefinish,andsoforth.

Dimensionsinengineeringdrawingsareshowninunitsoflengthandangle.The standardunitof length inSI system is themeter. Indrawingpractice, thepreferred SI unit of length is themillimeter.Onemeter (1m) is equal to onethousandmillimeters (1,000mm). Fractions in dimensions are not allowed inmetricdrawings;onlydecimalvaluesareallowed.Architecturaldrawingsmaybedimensionedinmillimeter(mm)andmeters(m).Metersandkilometers(km)areusedforcivildimensioning.

Angle refers to the relative orientation of lines on a plane or the relativeorientationofplanesinspace.Angleisconventionallymeasuredindegrees(°).Thereare360degrees inacircle;60minutes inadegree;and60seconds inaminute.ThedegreeisthecommonunitofangularmeasureinmetricandEnglishdrawings.

DEFINITIONS

Adimensionisanumberinastandardunitofmeasureshownonadrawingtoindicatesize,location,ororientationofgraphicfeatures.Adesignsize is the functional sizeof anobject and is equal to the full-sizevalueoftheobject.

•

•

•

5.3

1.2.3.4.5.6.

Aplotorprintsizeistheactualsizeofagraphicentityonaphysicaldrawingsheet.Tolerances are small variations permitted on functional sizes for ease ofmanufacture.Actual size is the size of a manufactured object obtained throughmeasurements.

Notethatonlydesignsizesareshownasdimensionsinengineeringdrawings.Plotsizesarenotshown,butascalefactorisusuallyindicatedonthedrawing.Thescalefactoristheratiobetweenthedesignsizeandtheplotsize.Tolerancesare required for manufacturing convenience because some errors must beaccommodatedduringmanufacturingandareusuallyintheone-hundredthsandone-thousandthsoffunctionalsizes.

DIMENSIONELEMENTSANDSYMBOLS

Figure 5.1a shows several elements that define a dimension in engineeringdrawings.Theseelementsare:

Graphicfeature(lineinFigure5.1a)ExtensionlineDimensionlineterminatorDimensionlineDimensionvalue(number)Visiblegap

Figure5.1.Dimensionalelementsandterminators.(a)Elementsofadimension.(b)Dimensionlineterminators.

ThegraphicfeatureinFigure5.1arepresentsadimensionalentityinaviewofadrawing. Itmaybea line,arc,circle, fillet,andsoon.Theextension lineconnectstheobjectfeaturewiththedimensionline.Sometimes,leadersareusedin place of extension and dimension lines, especiallywhen dimensioning arcsandcircles.

Thedimensionlineterminatorsindicatethelimitsofadimension.Theyoccurinpairs,oneateachendofthedimensionline.Itisafilledarrowinthisfigure,but it could be an unfilled arrow, an open arrow, a slash (/), or a filled smallcircle (●), as shown inFigure5.1b.Thedimension line is alwaysparallel toalinefeatureinanobject,butperpendiculartotheextensionline.Thedimensionvalueisanumberrepresentingthesizeofthedimension.Often,itisplacedinagap on the dimension line that is broken to allow this type of placement.However,itmaybeplacedaboveorunderthedimensionline.Itiseasiertoreadondrawingswhenplacedhorizontally.Thevisiblegapisaspacethatdemarcatesthe object feature from dimensional elements. This is very important indimensionplacement.

Table5.1showsomedimensioningsymbolscommonlyassociatedwithbasicdimensioning. These symbols have been standardized so as to eliminatelanguage translation.Thismakes it possible fordrawingsprepared indifferent

5.4

countries tobe readand interpretedcorrectly.Figure5.2 showsadimensionedcomponent;howmanydimensioningsymbolscanyouidentifyinit?

DIMENSIONTYPESANDLINESPACING

A dimension may describe size, location, or orientation (angle) of a feature.Figure5.3showsthebasictypesofdimension:S-size,L-location,andA-angle.Thesizedimensiongivesthedesignsizeofafeature.Alocationdimensiongivesthedistance(s)ofakeypointonafeaturefromareferencepoint,line,orplane.For example, the center point of a circle is a key point commonly used indimensioning the location of the circle. An orientation dimension gives theangularpositionofonefeaturerelativetoanother.Beveledandslopingfeaturesare common inmanycomponents.Theorientationof the facesonwhich suchfeatures appear need to be dimensionedwith the size of the angles associatedwiththeorientations.

Table5.1.Commondimensioningsymbols

Figure5.2.Dimensionedcomponent.

5.5

Figure5.3.Typesofdimensions.

Figure5.4.Spacingofdimensions.

Figure5.4showstherecommendedminimumgapsfordimensionplacementbyANSI/ASME standard. The first dimension line should be at least 10mm(0.375in)fromavisibleoutline,others6mm(0.25in)fromthenextdimensionline. Larger dimensions should be placed over smaller ones, as indicated inFigure5.4.

PLACINGDIMENSIONSONOBJECTFEATURES

Placing dimensions on the features of an object on a view must be done

1.2.3.4.

5.6.

7.8.

9.

10.

11.

12.

13.

14.15.16.17.

18.19.20.21.22.

systematically and with thoughtfulness. The overriding concern is to presentdimensionswithclarity.Athoughtabouthowthedimensionmaybeverifiedbymeasurementorinspectionshouldbeconsideredwhenplacingdimensions.Thefollowingguidelinescanbehelpfulwhendimensioning:

Therearetwotypesofsizes,namely,linearandangular.Usevisiblelinesonlyfordimensioningfeatures.Donotusehiddenlinesfordimensioningfeatures.Spacingbetweenthevisibleoutlineandfirstdimensionlineshouldbeatleast10mm(3/8in).Spacingbetweenadjacentdimensionlinesshouldbeatleast6mm(1/4in).Provide a visible gap between the extension line and the feature beingreferenced.Placedimensionoutsideviews,exceptithelpsclarityplacingtheminside.Somefeatures(e.g.,circles,arcs)havetwotypesofdimensions,namely,sizeandlocation.Sizeandlocationdimensionsofcirclesandarcsshouldbeplacedintheviewrevealingtheirtrueshape.Dimensions common to two views should be placed between the views,exceptwhenclarityisimpaired.Afeaturedimensionshouldbeshownonlyonceinadrawing.Noduplicationofthedimensionofthesamefeature.Dimensionsofdifferentfeaturesofthesamesizemustbeshownindividuallyonce.Dimensions of identical or similar features that are equal should be shownwiththerepeatedsymbol.Useofreferencedimensionsshouldbeminimizedoravoidedcompletely.Dimensionsshouldbegroupedtogetherasmuchaspossible.Minimizeextensionlinescrossingthemselvesorvisiblelines.Dimensionvaluesshouldnotoverlapthemselves,dimensionlines,extensionlines,orvisiblelines.Dimensiontextshouldbehorizontal;itiseasierreadinghorizontalnumbers.Smallerdimensionsshouldbeplacedinsidelargerdimensions.Minimizeoravoidleaderlinescrossingdimensionorextensionlines.Leaderlinesshouldbeinclinedat15oto75o;but30oto60oispreferred.Use datum dimensioning. Avoid chain dimensioning, especially formechanicalobjects.

5.5.1 DIMENSIONINGARCSANDCIRCLES

Figure5.5showsthedimensioningofarcs.Arcsshouldbedimensionedontheviewrevealingthearccontour.ThesymbolRforradiusmustprecedethevalueof thedimensionofanarc. If thecenterpointofanarc isnotobvious, then itmust be shown by dimensions. Figure 5.6 shows the dimensioning of circles.ThesymbolØfordiametermustprecedethevalueofthedimensionofacircle.ThecenterpointofacirclemustbedimensionedforlocationreasonsasshowninFigure5.6.Figure5.7showsdimensionplacementsforthediametersofsomeobjects.NoticethattheinformationintwoviewsinFigure5.7a ispresented inoneviewinFigure5.7bbecausethesectionviewallowsdirectdimensioningofthebore.Figure5.7ccouldbesectionedalso.

Figure5.5.Arcdimensions.

Figure5.6.Circledimensions.

Figure5.7.Dimensioningdiameters.(a)Diameteronprofileview.(b)Section

5.5.2

5.5.3

5.5.4

viewshowingdiameter.(c)Multiplediametersonprofileview.

DIMENSIONINGANGLES

Figure 5.8 shows the dimensioning of angles. Angular dimensions should beexpressed in degrees, minutes, and seconds or the decimal equivalent. Inmechanicaldrawings,anglesarespecifiedindecimalunits.

DIMENSIONINGHOLES

Figure 5.9 shows one through hole and one blind hole. Holes should bedimensionedontheviewshowingthecircleoutline.Thedepthofthroughholesis not specified on a drawing; however, the depth of a blind hole must bespecified either by the depth symbol or directly by the size. The depth of theblindholeinFigure5.9isspecifiedasareferencedimensionforinterpretationofthedepthsymbolonthetopviewonly;itshouldbeomittedinpracticebecausethedepthsymbolisusedonthetopview.

Figure5.8.Angulardimensions.

Figure5.9.Holedimensions.

DIMENSIONINGSLOTS

5.5.5

Slotsarecommonfeaturesonshaftsandothercomponents.Properdimensioningof slots depends on their function and form. Length shown may be betweencenters(Figure5.10a)orfulldependingonwhichiscritical(Figure5.10b).Iftheend radii are larger than the width of the slot, they should be shown (Figure5.10c).

DIMENSIONINGFILLETSANDROUNDS

Figure5.11showsafilletandaround.Filletsandroundsarearcs thatprovidefor the smooth transition of faces on an object. They help in removing roughedges,andreducestressintensificationassociatedwithgeometricdiscontinuitiesinmechanical components. Fillets are used for interior faces and are concavearcs.Roundsareusedforexteriorfacesandareconvexarcs.Filletsandroundsshouldbedimensionedon theviewrevealing thearcasshown inFigure5.12.ThesymbolR forradiusmustprecedethevalueof thedimensionofafilletorround.Whenthereareseveralfilletsandroundsofthesamesizeonanobject,itis common for the size to be specified in a local note such as “All fillets androunds=3mm.”

Figure5.10.Dimensioningslots.(a)Fulllength.(b)Lengthbetweencenters.

Figure5.11.Filletsandrounds.

5.5.6

5.5.7

Figure5.12.Filletsandroundsonacomponent.

CHAMFERDIMENSIONS

Figure5.13showsexternaland internalchamfers.Chamfersarebevelededgesonobjects,andtheymakeassemblyeasier.Chamfersmaybespecifiedbynotesor dimensions as shown in Figure 5.13a for external chamfer. The setbacklengthsonthehorizontalandverticaldirectionsareusedtospecifyachamferbydimensions. The horizontal length is given first (right end of Figure 5.13a).Alternatively, the horizontal setback length and angle may be used forspecification(leftendofFigure5.13a).Figure5.13bshowsthedimensioningofaninternalchamfer.Noticethat threedimensionsareneededin theformat: theincluded angle, setback, and small diameter.Half of the included angle couldhavebeenused instead. If thespecificationornote format isused, thesetbackandhalfincludedanglearesufficientfordimensioning.

Figure5.13.Chamfers.(a)External.(b)Internal.

DIMENSIONINGCOUNTERBORES,COUNTERSINKS,ANDSPOTFACES

Figure5.14 shows featuresof a counterbore, countersink, and spotface.Pleasetake time to study the symbols associated with each feature in this figure. Acounterboreisacylindricalrecessonafaceofanobject.Itismadebyenlargingsmallerholeswithaboringtool.Forthecounterborefeature,Φ30referstothesizeofthethroughhole,Φ40referstothesizeofthestephole,andsize20refersto thedepthof thestephole.Acountersink isaconical recessona faceofan

5.5.8

object. It ismadewitha special toolandmaybeusedas seats for screwsandcentersforcylindricalcomponentslikeshaftsandspindles.Forthecountersinkfeature,Φ30referstothesizeofthethroughhole,Φ37referstothesizeofthetaperedholeatthesurfaceofthepart,and82°refertotheincludedangleofthetapered hole. A spotface is like a counterbore, except that the depth is muchsmaller.Theyactasseatsforwashersandscrewheads.Forthespotfacefeature,Φ30referstothesizeofthethroughholeandΦ60referstothesizeofthestephole. Notice that the depth of the spotface is not specified. This is because aspotfacetoolismanufacturedforspecificdepth,oftennotmorethan2mm.

DIMENSIONINGKEYSEATSANDKEYWAYS

Keyseatsareexternalslotsonshafts,axles,andsoonthatacceptkeys.Keywaysareinternalslotsonhubsofcranks,levers,gears,pulleys,sprockets,andsoon.Figure5.15showsakeyseatandakeyway.Dimensionsshouldbeplacedsuchthatmeasurementorinspectionofkeyseatsorkeywayscaneasilybecarriedout.The lengthof thekeyseatshouldbeshownon the longitudinalview.Abrokensection is commonly employed for this, as shown in Figure 5.16 where threetypesofkeyseatsareindicated.Ifthekeyseatdoesnotstartorendattheedgeoftheshaft,thelocationdimensionmustbeincludedasshowninFigure5.16aandFigure5.16b.

Figure5.14.Dimensioningcounterbore,countersink,andspotface.

Figure5.15.Keyseatandkeyway.

5.5.9

5.5.10

Figure5.16.(a)Regularkeyseat.(b)Woodruffkeyseat.(c)Sledgerunnerkeyseat.

DIMENSIONINGNECKSANDUNDERCUTS

Necks and undercuts are used to alleviate the influence of stressconcentrationandrelievetheendsofthreads.Necksarecommononcylindricalsections,whileundercutsareusedonfaces.Therearerectangular,circular,andtruncatedconicalnecksorundercuts andare shown inFigures5.17,5.18, and5.19, respectively. The sizes of these features are specified by the width anddepth, thewidthvalueprecedingthedepthvalueas indicatedinFigures5.17a,5.18a,and5.19a.Alternatively,thediametervalueofthenecksectionisgivenasshown in Figures 5.17b, 5.18b, and 5.19b. This is the preferred method fordimensioningnecks andundercuts because they canbemeasuredor inspectedeasilythisway.

DIMENSIONINGREPEATEDFEATURES

Somefeatureslikeholesarerepeatedoncomponents.Eachfeatureshouldnotbedimensionedseparately;instead,thelocationandorsizeforoneofthefeaturesshouldbeindicated,andthen,thetotalnumberisincluded.Figure5.20ahasfourholesspacedequallyinalineararray.Thoughtherearefourholesorcircles,thenumber of equal spacing between the circles is three (3) as indicated. Figure5.20b has six holes spaced equally on a circle diameter in a radial array. Thelowercircleinthefirstquadrantislocatedbythe30°angle,circlespacingis6innumber(6×60°),not5,aswouldbeexpectedinalineararray.

5.6

Figure5.17.Rectangularneck.(a)Depthspecified.(b)Diameterspecified.

Figure5.18.Circularneck.(a)Depthspecified.(b)Diameterspecified.

Figure5.19.Truncatedconicalneck.(a)Depthspecified.

Figure5.20.Repeatedfeatures.(a)Lineararray.(b)Polararray

DIMENSIONINGMETHODS

Threemethodsofdimensioningareincommonpractice.Thesearedatum,chain,and tabular.Thedatummethod is depicted inFigure5.21 and is preferred formechanicaldrawings.Adatummaybeapoint,line,orsurfaceonacomponentthatisassumedtobeexact.Itisusedasareferenceforlocatingotherfeaturesonthecomponent.Adatumpointisoftenchosenatthebottom-leftpointonapartin view. The chain method is illustrated in Figure 5.22 and is popular in

architecturaldrawings.Thismethodisnotrecommendedformechanicalparts.

Figure5.21.Datumdimensioning.

Figure5.22.Chainmethod.

The tabularmethod isshowninFigure5.23and isused in industry tosavespaceandprovide informationclearlyandconcisely, saving timeandeffort. Itconsists of a diagram dimensioned using letters and a table where values areassignedtotheletters.Tabulardimensioningisverycommonintechnicalsalescatalogs.

Table5.2.Valuesofdimensions

Size 2 4 6

A 6.5 10 12.5

B 0.875 1.25 1.4375

C 2.75 3.375 3.875

5.7

Figure5.23.Tabularmethod.

DIMENSIONSTYLE

WhendimensioninginCDDenvironment,textstylesanddimensionstylesareagreat advantage. A text style defines a set of character attributes for specificapplications.Adimensionstyledefinesasetofattributesfordimensiondisplayin specific applications such as mechanical, civil, or architectural. Therecommendedtextheightforthedimensionvalueis3mm(0.125in),butspaceconsiderationmayrequireasmallerfontsize.Table5.3givessomeattributesofthe dimension style. Some other attributes are suggested as proportions of thefontsizeortextheight.

Tosetupadimensionstyle,itisadvisabletocreateatrialdimensionsoastojudgethesuitabilityofthedefaulttextheight.Thecomputerscreensizeoftextdependsonthesizeofadrawing,soonedimensiontextheightwillnotworkforeverydrawing.Sometimes,thedimensiontextmayappeartoosmallortoobigwiththedefaultfontsize,andthetrialdimensioneasilyrevealsthis.Atrial-and-errorapproachmaybeusedtoadjustthetextheighttoasuitablevalue.Theruleof twoor threecanbeusedwhenadjustingscreen textheight.Onceasuitabledimension text height is arrived at, then the dimension style setup can becompletedusingtheproportionssuggestedinTable5.3.Theadjustmentshouldbemade in the dimension style dialog box, so that the changes can apply tosubsequentdimensions.

Table5.3.Somedimensionstyleattributes(AutoCADapplication)

Attribute Value

Dimensionunit Metric/English

Dimensiontextfontorstyle Simplex(suggested)

Textheight h0

Arrowstyle Closedblank

5.8

5.8.1

Step1:1.2.3.

Arrowsize ≥h0

Extensionlinecross-over h0

Extensionlineoffset(gap) h0

Dimensionvaluelocation Centered

Dimensionvalueorientation Horizontal

Dimensionvaluelocationgap 0.5h0

MANUALDIMENSIONING

ModernCDDpackages are becoming automated in the generation of drawingviews and dimension placement as they are progressively being improved.Asthe capabilities of solidmodeling software increase, designers, architects, andengineerswillberequiredtododraftingtasks.Printcheckingandreadingwillbecomedominantskillsfortechnologypersonnelbecausetheywillberequiredin interpretingandensuringqualityassuranceofcomputer-generateddrawings.Therefore, drafting skills will still be relevant in the automated draftingworkplace,especiallyannotationskills.

MANUALDIMENSIONPLACEMENT

ManualdimensionplacementinvolvesaddingdimensionalvaluesoneatatimebyaCDDuser.Theprocedurefordimensionplacementisvirtuallythesameaswouldbedoneintraditionaldrafting,exceptthattheCDDuserhasthecomputerto his or her advantage. In either case, engineering diagrams must be readybefore dimensions can be placed. The drawing views should be reviewed andchecked for correctness before placing dimensions on them. Correcting plaindrawing errors after placing dimensions is tedious and time-wasting even in aCDDenvironment.Inthisexample,dimensionswillbeplacedmanuallyusingaCDDpackage.Thestepsforthetaskofdimensionplacementareoutlinednext.

Createtheplaindrawing:UseCDDpackageroutinetogeneratedrawingviews.Addhiddenlinesifnecessary.Addcenterlinesifnecessary.

Figure5.24istheplainmultiviewdrawingofacomponentgeneratedfromasolidmodel.Theisometricinsertisincludedforcompletenessandvisualization.

Step2:1.2.3.

Step3:1.

2.Step4:

1.2.

There is need to provide a good gap between views to make room to thedimensions.

Figure5.24.Engineeringdiagramofacomponent.

Setupthedimensionstyle:Createtrialdimension.AdjusttrialdimensionfontsizeifnecessaryUsedimensionstyledialogboxtocompletesetup

Addhorizontaldimensions:Add horizontal sizes on top and front view or top and right viewfeatures.Figure5.25showstheaddedhorizontaldimensionstoFigure5.24.

Addverticaldimensions(frontandrightview,topview):Addverticalsizesontopandfrontviewortopandrightviewfeatures.Figure5.26showstheaddedverticaldimensionstoFigure5.25.

Figure5.25.Addinghorizontaldimensionstodiagram.

Step5:

1.2.

Step7:1.

2.Step8:

1.Step9:

Figure5.26.Addingverticaldimensionstodiagram.

InFigure5.26,dimensionscommontofeaturesonadjacentviewshavebeenplacedbetweentheviews.Thisistherecommendedpractice.Thedimension50in the top view may be omitted because it is obvious by visual inspection.However, it isalwayspreferred toexplicitlyspecifydimensions inengineeringdrawings

Addangulardimensions(notapplicableinthisexample).Step6:Addarcandcircledimensions:

Addcirclesizestotopandrightviews.Figure5.27showsthecircledimensionstoFigure5.26.

Note that only one of the two circles in the right view of Figure 5.27 isdimensionedwith the 2×multiplier added. The 2× is indicative of a repeatedfeature,twiceinthiscase.Thoughthisexampledoesnotpresentallthefeaturesin drafting practice, the principles of dimensioning are the same.When theseprinciplesareconsistentlyapplied,goodannotateddrawingswillresult.

Checkdrawingdimensions:Checkallarcandcircle features for locationdimensions(threeholesandaboss).Checkalldimensions(verifysizeandlocationdimensions).

Addnotes:Notincludedinthisexample.

Generatecheckprintforreview:

1.2.3.

5.9

Figure5.27.Addingcircledimensionstodiagram.

Printthedrawing.Carefullycheckforcorrectnessandcompletenessofdimensions.Makecorrectionsasneeded.

Itmaysurpriseyouwhatyoudiscoverinacheckprint,especiallyasanewperson in the fieldofdrafting.Never turn inadimensioneddrawingwithoutathorough check on the layout of views and placed dimensions. Errors indimensional values are hardly tolerated because of associated production cost,rework,andcompanyimage.

CDDAUTOMATICDIMENSIONPLACEMENT

SomesolidmodelingCDDpackageshaveroutinesforaddingbasicdimensionsautomatically to the plain drawing views that are generated from the solidmodels.Dimensionsfromthesolidmodelthatcanbeautomaticallyretrievedarethoseexplicitlydefinedduringtheconstructionofthesolidmodel.Anyrelevantdimensionnotdefinedinthesolidconstructionwillhavetobemanuallyaddedlater.InsomeCDDsoftware,angulardimensionsarenotretrievedfromthesolidmodel, so theywill have to bemanually added. The positions of some of theretrieveddimensionsmaynotbesatisfactory.Hence,someformofmanualfine-tuning will normally be necessary after automatic centerline and dimensionplacementroutineshavebeenused.Intheprevioussection,theemphasiswasonmanualskillsinbasicdimensioning.Inthissection,advantagewillbetakenofautomatic annotations routines of CDD software. Taking note of the pointshighlightedpreviously, thestepsfor thedimensioningtaskareoutlined.Again,

Step1:

Step2:

Step3:

solidedgeisusedinthisexample.

Generatedrawingviews:Letususe the samecomponentof theprevious section.Using theviewplacement routine, generate the drawing views for the component fromthe solid model as shown in Figure 5.28. Ensure that enough space isprovided between views tomake room to the dimensionswhen placingtheviews.Addcenterlines:AscanbeobservedinFigure5.28,hiddenlineswereaddedtotheviewswhen theappropriate routinewasused.Centerlinesneeded tobeadded.The CDD software used here has a routine for automatic centerlineadditiontotheviews.Afterapplyingthisroutine,plaindrawingviewsareobtainedasshowninFigure5.28.Adddimensions:UsingtheroutineoftheCDDsoftwareforautomaticdimensionadditiontotheviews,thedimensionswereaddedtotheviewsofFigure5.29withtheresultofFigure5.30.

Figure5.28.Generatedviewsofacomponent.

Figure5.29.Addcenterlinestogeneratedmultiviews.

Step4:

(a)

(b)(c)

(d)

(e)

(f)

Figure5.30.Addingdimensionstomultiviewdrawing.

Add missing dimensions and fine-tune dimension positions andplacements.AlookatFigure5.30willshowthat:

The positioning of the dimension of the small circle in the top viewneedsadjustmentforclarity.Thepositioningofdimension100inthefrontviewneedsadjustment.Thedimensions35and30 in the frontviewarechained.This isnotrecommendedformechanicalcomponents;therefore,re-dimensioningisnecessary.Thetwocirclesintherightviewhavenosizedimensions.Theymustbeadded.The twocircles in the rightviewhaveno locationdimensions.Theymustbeadded.Figure5.31isthefine-tuneddimensioningofFigure5.30.

Adrawing suchas thatofFigure5.27orFigure5.31 is partially annotatedbecause it lacks tolerances and possibly some vital specifications onmaterial,finishes,heat treatment,andsoon.That is, theyarenotworkingdrawingsyet.WorkingdrawingsarediscussedinChapter7.

5.10

1.2.3.4.5.

6.7.8.9.10.11.12.13.14.

5.11

Figure5.31.Dimensionedmultiviewdrawing.


Definedesignsize,actualsize,andplotsize.Whatisadimension?Whatarethetwobasicsizedimensions?Whatisalocationdimension?Howisitdifferentfromasizedimension?The U.S. national standard for dimensioning practice is defined in whatdocument?Whichviewshouldarcsandcirclesbedimensioned?State10principlesofdimensioningmentionedinthischapter.Whydoyouthinkclarityisimportantduringdimensioning?Shoulddimensionsalwaysbeplacedoutsideadrawingview?Shouldyouavoidoverlappingofdimensionandextensionlines?Whatarethestylesusedindimensioningslots?Whatarethestylesusedindimensioningundercuts?Whatarechainandbaselinedimensioning?Whichmethodisnotrecommendedformechanicaldrawings?

CHAPTEREXERCISES

Create the top, front, and right views of the following figures and add

dimensions.



6.1

6.2

CHAPTER6

ISOMETRICDRAWINGS

INTRODUCTION

Isometricdrawingsareatypeofpictorialdrawingsthatshowthethreeprincipaldimensions of an object in a single view. The principal dimensions are theoverall sizes for the object along the three principal directions. Pictorialdrawingsconsistofvisibleobjectfacesandthefeatureslyingonthefaces.Theinternal featuresof theobjectare largelyhidden fromview.Pictorialdrawingstend to present images of objects in a form thatmimicswhat the human eyewouldseenaturally.Nontechnicalpersonnelcaninterpretthembecausetheyaregenerallyeasytounderstand.Pictorialdrawingsareanexcellentstartingpointinvisualizationanddesignandareoftenusedtosupplementmultiviewdrawings.Hidden lines are usually omitted in pictorial drawings, exceptwhere they aidclarity.

Anisometricdrawingisoneofthethreetypesofaxonometricdrawings.Itiscreated on the basis of parallel projection technique. The other two types ofaxonometric drawings are dimetric and trimetric drawings. In isometricdrawings,thethreeprincipalaxesmakeequalangleswiththeimageplane.Inadimetric drawing, two of the three principal axesmake equal angleswith theimageplane,whileinatrimetricdrawing;thethreeprincipalaxesmakedifferentangleswith the imageplane. Isometric drawings are themost popular and areeasier to construct than the others. Some computer design drafting (CDD)packagescangeneratesallthreetypesofviews.

ISOMETRICPROJECTIONANDSCALE

An isometric projection is a representation of a view of an object at 35°16’(35.27°)elevationand45°azimuth.Theprincipalaxesofprojectionareobtainedbyrotatingacubethrough45°aboutaverticalaxis,thentiltingitdownwardat35°16’asshowninFigure6.1a.Adownwardtiltofthecubeshowsthetopface,whileanupwardtiltshowsthebottomface.The45°rotationismeasuredonahorizontal plane, while the 35°16’ angle ismeasured on a vertical plane. Thecombinedrotationsmakethetopdiagonalofthecubetoappearasapointinthefront view.The nearest edge of the cube to the viewer appears vertical in theisometricview.The tworecedingaxesproject fromtheverticalat120°on theleftandrightsidesoftheverticalline,asshowninFigure6.1b.Thesethreeaxesformtheprincipalaxesandareparalleltothecubeedgesintheisometricview.The two receding axes are inclined at 30° to the horizontal line, while theverticalaxisisat90°tothehorizontal line.Thethreevisiblefacesofthecubeare on three planes called isoplanes and are referred to as left, right, and topisoplanes. The front view of objects is commonly associated with the leftisoplane, the right viewwith the right isoplane, and the topviewwith the topisoplane. Lines on an object parallel to the isometric axes are referred to asisometriclines,whilelinesnotparalleltothemareknownasnonisometriclines,as shown in Figure 6.2a. Isometric projection is not the most pleasant to thehumaneye,butitiseasytodrawanddimension.

Figure6.1.Isometricprojection.(a)Isometricrotations.(b)Isometricaxesinimageplane.

In pictorial projection, the regular axis is usually inclined at 45°, but thereceding axes in an isometric projection are inclined at 30° to the horizontal.Hence, there is a difference inorientationbetween the receding isometric axisandtheregularaxis.TheseorientationsofaxesareshowninFigure6.2b,whereameasurementof 10units along the regular axisprojects to8.16units on theisometric axis. Thus, one unit ofmeasurement on the regular axis is equal to0.816ontheisometricscale.Thismeansthataregularlengthofoneunitmustbescaledto0.816unitsinanisometricprojection.

Now, isometric projection is an accurate representation of an object on the

6.3

isometric scale, that is, whenmeasurement is made along the isometric axes.Thisisabout18percentshortoftheactualdimensionsoftheobject.Inpractice,a regular length of one unit is drawn as one unit on the isometric axis, thusintroducing some error to the projection. Hence, the actual images of objectshown in isometric views are called isometric drawings, and not isometricprojections. The main difference between an isometric projection and anisometric drawing is size. The drawing is slightly larger than the projectionbecause it is full scale. Features in isometric drawings may be created onisometricplanesornonisometricplanes.Forfeaturesonnonisometricplanes,itwillbehelpfultofirstcreatethemonisometricplanesandthenprojectthemtononisometric planes during construction of isometric drawings. Please refer toFigures6.10to6.13.

Figure6.2.(a)Typesofisometriclines.(b)Isometricscale.

TYPESOFISOMETRICDRAWINGS

Isometricaxescanbepositionedindifferentwaystoobtaindifferent isometricviewsof anobject.Threebasicviews are ingeneral use, and they are regularisometric,reverseisometric,andlong-axisisometric,asshowninFigure6.3.Inregularisometric,theviewerlooksdownontheobject,sothetopoftheobjectisrevealed.Therecedingaxesaredrawnupwardtotheleftandrightat30°fromthe horizontal. The nearest end of the object is at the lower front base of theboundingbox(B-box),asshowninFigure6.3a.Thisisthemostcommontypeof isometric drawing. The viewer in reverse isometric is looking-up at thebottomoftheobject,sothisviewrevealsthebottomoftheobject.Therecedingaxesaredrawndownwardfromthehorizontalat30°withthelowerbackendatthebaseoftheB-box,seeFigure6.3b.Thelong-axisisometrickeepsthelargestprincipal dimension of the object horizontal as one principal axis. This isnormally used for objects with length considerably larger than the width ordepth.Theviewpointcouldbefromthe leftor rightsideof theobject,but the

6.4

Step1:

Step2:

long axis is drawn horizontal and the others are drawn at 60°, as indicated inFigure6.3c.Thelong-axisisometricistheleastused.

Figure6.3.Typesofisometricdrawings.(a)Regular.(b)Reverse.(c)Long-axis.

CONSTRUCTINGISOMETRICARCSANDCIRCLES

Arcs and circles are common features on objects, especially in mechanicaldesigndrafting.Isometricarcsareportionsofisometriccirclesthatareellipseson isometricplanes.Figure6.4 showsa componentwith isometric arcson theright face or right isoplane. As the arcs are portions of isometric circles, thetechnique for creating isocircles will be discussed. It is worth noting that anisometric arc can be constructed without creating a full isometric circle. Oneimportantruletorememberwhencreatingcurvesinisometricprojectionisthattheisometricfaceonwhichthecurveslieonshouldbecreatedfirstusingguideor construction lines. Then, the curves can be created using projection of keypointsandintersectionofprojectionlinesfromthekeypoints.Asecondruleisthat true dimensions are transferred to nonisoplanes. Hence, where there areinclined and oblique faces, the true sizes of features on the auxiliary viewsshould be used during construction.There are several techniques available forcreatingisocircles,butaneasyandmorepopularoneis thefour-centerellipse.Thefour-centerellipseisanapproximateellipse,but it isusuallygoodenoughformostdraftingapplications.Figure6.5showsinfivesteps,thecreationofthetopisocircle.

Drawasquareusingthecirclediameterassize:For the top isocircle, the top isoplane is the right surface to draw thesquare.ThetopisoplaneishorizontalascanbeseeninStep1ofFigure6.5.Drawtheisometricsquare.Drawthecenterlinesofthesquare:DrawthetwocenterlinesofthesquareasshowninStep2ofFigure6.5.

Step3:

Step4:

Step5:

Drawthebigarcsoftheisocircle:Identify the key points K1 and K2. These are two centers of the four-centerellipsetechnique.Noticethatthesecentersarelocatedattheobtuseanglecornersoftheisometricsquare.UsingtheradiusR,withcentersatK1andK2,drawthetwobigarcsfortheisocircleasshowninStep3ofFigure6.5.

Figure6.4.Isometricarcs.

Locatethecentersofthesmallarcsoftheisocircle:DrawthediagonalK3-K4betweentheacuteanglecornersofthesquareinFigure6.5.Then,drawlinesK1-K5andK2-K6.Theintersection(K7)ofthelinesK3-K4andK1-K5inStep5locatesonecenterforasmallarc.Theothersmallarccenter is locatedatK8, the intersectionof linesK3-K4andK2-K6.Drawthesmallarcsoftheisocircle:UsingthecentersofthesmallarcsK7andK8,drawthetwosmallarcsofradius r,asshowninStep5ofFigure6.5.Verify that thebigandsmallarcsaretangenttotheisometricsquare.IfaCADpackageisused,circlescould be drawn instead of arcs. The circles must then be trimmed toobtainthearcsrequiredintheisocircle.Figure6.6andFigure6.7show,respectively,infivesteps,howtheleftandrightisocirclescanbecreated.These steps are the same as described earlier in Figure 6.5 for the topisocircle, except that the isoplanes are, respectively, the left and rightones.

Figure6.5.(a)Constructingtopisocircle.(b)Constructingtopisocirclescontinued.

Figure6.6.Constructingaleftisocircle.

Figure6.7.Constructingarightisocircle.

6.5

6.5.1

The construction of isometric arcs follows the same steps as isocircles asdescribed.However,aquickvisualinspectionofthearcinaproblemwillrevealwhichquadrant(s)thearcislocatedin.Quarterarcsandhalfcirclearcsarequitecommon inmechanical drafting.For example,Figure9.4has a quarter arc onone of the acute angle corners, requiring the construction of one of the smallradiusarcsinanisocircle.

Thefivestepsdescribedpreviouslyforcreatingisocirclescouldbereducedtothree, as shown in Figure 6.8 by combining Steps 1 and 2 as Step 1; andcombiningSteps3(withoutdrawingthelargearcs)and5asStep3.ThisleavesStep4asthenewStep2inwhichallthekeypointsK1toK8arecreated.ThecentersofthefourarcscanthenbeidentifiedasK1,K2,K7,andK8.Inthelaststep(newStep3),thefourarcsarecreated,asshowninFigure6.8.

Figure6.8.Constructingtopisocircle.

CONSTRUCTIONTECHNIQUESFORISOMETRICDRAWING

It is quite easy creating isometric lines on isometric planes. This is done bydrawing the lines parallel to isometric axes. However, creating non-isometriclinesandanglesmustbedonewithcare.Ingeneral,anglesofnonisometriclinesaredrawnbycreatinglinesegmentsbetweentheendpointsofthelocationsthatformtheangle.Irregularcurvesarecreatedfromintersectionsofprojectionlinesfromisometricplanes.Thetwocommontechniquesgenerallyusedforisometricdrawingsaretheboxandthecenterlinelayouttechniques.

BOXTECHNIQUEFORISOMETRICDRAWINGS

The box technique is the most common construction technique and is alsoknownasthecoordinatetechnique.Intheapproach,abounding(B-box)isfirstmade with guide lines using the principal dimensions on the object. TheprincipaldimensionsmaybedesignatedasWforwidth,Hforheight,andDfor

1.2.3.

4.5.

6.5.2

6.5.3

depth.Itmaybenecessarytoadd-updimensionsalongtheprincipalaxestogettheprincipaldimensionsofanobject.Thefacesontheobjectsarethencreatedafter the B-box is ready. Each feature on the object is properly located andcreated within the B-box. This technique is good for drawing objects withangular and radial features or objects that have irregular shapes or form. Thegeneralstepsintheboxtechniqueare:

Definetheoriginofandcreatetheisometricaxes.Createtheboundingboxusingtheprincipaldimensions.a.Usedimensionsfromtopandfrontviewtomarkoutfaces.b.Or,usedimensionsfromtopandsideviewstomarkoutfaces.Locateandcreateallfeaturesonthefaces.Finishandcheckthedrawing.

OBJECTWITHNORMALFACES

Figure 6.9 shows the construction of the isometric drawing of an object withnormalfaces.ThemultiviewdrawingoftheobjectisshowninFigure6.9a.NotethatStep4inthegeneralprocedureisnotneededforthisobject.

Steps1and2ofthegeneralprocedurecanbecombinedintoonebydrawingtheB-boxdirectly,keepingtheisometricaxesdirectioninmind.

OBJECTWITHINCLINEDFACES

Figure6.10 shows the constructionof the isometricdrawingof anobjectwithinclined face. Themultiview drawing of the object is shown in Figure 6.10a.Note thatStep4 in thegeneralprocedure requires thecreationofan isometriccircleontheinclinedface.

6.5.4

Figure6.9.(a)Boxmethodfornormalfaces.(b)Boxmethodfornormalfacescontinued.

Figure6.10.(a)Boxmethodforinclinedface.(b)Boxmethodforinclinedfacecontinued.

OBJECTWITHOBLIQUEFACES

Figure6.11 shows the constructionof the isometric drawingof anobjectwith

6.5.5

obliqueface.ThemultiviewdrawingoftheobjectisshowninFigure6.11a.Step4inthegeneralprocedureisnotrequiredinthisobject.

OBJECTWITHANGLEDFACES

Figure6.12 shows the constructionof the isometricdrawingof anobjectwithangledfaces.ThemultiviewdrawingoftheobjectisshowninFigure6.12a.Byinspectionof themultiviewdrawing, it isclear that the rightvertexon the topview is at themidpoint of the depth dimension D. This helps in locating thevertex on the B-box without using trigonometry. Observe that, with the frontangleof30°andthedimensionsWandW1given,thedimensionH1wouldnotbeshown.So,H1mustthenbecalculatedusingtrigonometry.Itcanbeshownthat:H1=H−(W−W1)× tan30°.Thus, the linesdefining theangleson theobject can be created on theB-boxwithout actuallymeasuring the angles 60°and30°.Alwaysrememberthatanglesonanobjectarenotdirectlymeasuredinisometric construction. They are used to calculate the end points of linesdefining the angles. Finally, note that Step 4 in the general procedure is notrequiredinthisobject.

Figure6.11.Boxmethodforobliqueface.

6.5.6

6.5.7

Figure6.12.Boxmethodforangles.

OBJECTWITHELLIPSEONINCLINEDFACES

Figure6.13 shows the constructionof the isometricdrawingof anobjectwithangledfaces.ThemultiviewdrawingoftheobjectisshowninFigure6.13a.Step1followsthegeneralprocedureandStep2createstheisocircleforthecylinder.InStep4,theinclinedfaceisdividedintosegmentsthatareusedtoprojecttheisocircleontotheinclinedfaceinStep5.Thesetwostepsareperhapsthemostchallenginginthisproblem.Careisneededtofirsttransferthesegmentstotheisocirclesoastodefinethekeypointsontheisocirclethatwillbeprojectedontothe inclined face. Then, the key points so established are transferred to theinclined face and the ellipse is created.Again, note that Step 4 in the generalprocedureisnotrequiredinthisobject.

Figure6.13.Boxmethodforellipseoninclinedface.

OBJECTWITHIRREGULARCURVES

Figure6.14showstheconstructionoftheisometricdrawingofanobjectwithanirregularcurve.Themultiviewdrawingof theobject isshowninFigure6.14a.Step1followsthegeneralprocedure.InStep2,thedimensionsshownonthetopviewofFigure6.14aareusedtomarkoutthekeypointsonthecurve.Itislikedividingthecurveintosegmentssothatenoughkeypointscanbegeneratedand

6.5.8

usedtoapproximatethecurve.Step3showsthecreationoftheirregularcurve.Again,notethatStep4inthegeneralprocedureisnotrequiredinthisobject.

Figure6.14.Boxmethodforirregularcurve.

CENTERLINETECHNIQUEFORISOMETRICDRAWINGS

Thecenterlinetechniqueisbetterforobjectswithmanycircularandarcfeatures.Thismethodbeginswithaconstructionofallthecenterlinesintheobjectusingthe top or bottom face as reference.Other features are added to complete thedrawing.Figure6.15showstheuseofthecenterlinemethodintheconstructionofanobject.Init,thefollowingstepsareoutlined:

Step1:

Step2:

Figure6.15.Centerlinemethodforisometricdrawing.

Createthecenterlines:Allcenterlinesintheobjectarecreatedandalignedwithisometricaxes.Thesizeoftheobjectwilldeterminethelengthofthecenterlines.Eitherthetoporbottomfaceoftheobjectcanbeusedasreference.ThebottomfacewasusedasreferenceinFigure6.15.Createisocirclesquares:On the centerlines drawn in Step 1, locate the centers of the isocircles.Usingthedimensionsavailable,drawthesquaresfortheisocirclesononefaceasshowninStep2ofFigure6.15.

Step3:

Step4:

Step5:

Step6:

6.6

Createarccentersforisocircleononeface:Usingthefour-centerellipsetechnique,create thecentersof thearcsfortheisocirclesononeface.Createisocirclesononeface:Once the centers of the arcs for the isocircles are finalized in Step 3,createthearcsforeachisocircle.Createisocirclesontheotherfaces:RepeatSteps2to4forotherfaces.FinishandcheckthedrawingComplete the drawing by creating connecting features to the isocirclesand removing lines and arcs that are hidden.Check that the drawing iscorrect.

ISOMETRICANNOTATIONS

Isometricannotationsconsistoftextualinformationaddedtoisometricviewsforcomplete documentation. These include dimensions, notes, tables, and so on.Annotations should be placed on isoplanes, and dimension lines should beparalleltoisometricaxes.Asmuchasispossible,keepalldimensionsoutsideofviewandshowdimensionsbetweenpointsonthesameplaneonly.Arrowheadheel should be parallel to the extension lines, and the dimension value shouldshowclearly.Thefront(forwidthdimensions)andright(fordepthdimensions)isoplanes are preferred for annotations. Figure 6.16a shows a box dimensionwiththepreferredformat;however,Figure6.16bshowsthesameboxdimensionwiththewidthanddepthsizesonthetopisoplane.Thisisalsoacommonformatforisometricdimensioning.Theheightdimensionsareplacedverticalandcouldbeonthefrontorrightisoplane.Thedimensionvaluecanbeplacedalignedwiththe dimension line or placed horizontally. Though the aligned placement isrecommended byANSI/ASME, the horizontal placement is common, perhapsduetorelativeeasewhendrawingmanuallyorsketchingfreehand.

6.7

6.7.1

Figure6.16.Isometricannotations.(a)Aligneddimensionplacement.(b)Horizontaldimensionplacement.

APPLICATIONSOFISOMETRICVIEWS

Isometric views are used in component and assembly drawings. Isometriccomponentpictorialsmaybepresentedintwoformats:isometricdetaildrawingor isometric insert view. Isometric detail drawing is a single viewwithproperannotations. Isometric insert view is an isometric viewof a component that isadded to necessary orthographic views principally to aid visualization andsometimesforcompletenessofdocumentation.Inassemblydrawings,isometricviews provide a general graphic description of each component in outline,exploded, and section views. Section pictorial views show all internalcomponents in mating position at a plane defined by the cutting plane line.Brokensectionisometricviewsareusedinassemblyanddetaildrawings.

ISO-DETAILDRAWINGS

Annotated isometric view of a component may be referred to as iso-detaildrawing. This is a single isometric view drawing of a component with allspecifications and dimensional information necessary for themanufacture andinspectionofthecomponent.Thisisdonemostlyforcomponentswithrelativelysimpleform.Figure6.17showstwoexamplesofiso-detaildrawings.However,sketched isometric views may be dimensioned during design development.Becausethesesketchesarenotdrawntoscale,theyarenotiso-detaildrawings,but may be called iso-detail diagrams. In orthographic detail drawings, it iscommoninpracticetohaveanisometricviewincluded,thoughannotationsarenotaddedtotheisometricview.

6.7.2

Figure6.17.Iso-detaildrawings.

ISOMETRICSECTIONANDEXPLODEDVIEWS

Different typesof sections in isometricviewscanbecreated,but the commononesarethestraight(full),half,broken,andoffsetsections.Objectsofirregularinteriorsaregoodcandidatesforisometricsections.Hatchlineinclinationshouldbe chosen with care to ensure that they are not parallel to isometric lines orfeature lines.A60° inclination forhatchpatterns is a commonpractice.Otherangles should be used where this is not appropriate. Figure 6.18a and Figure6.18b show examples of isometric full section and half section, respectively.Figure 6.18c and Figure 6.18d show examples of isometric broken and offsetsections,respectively.

6.7.3

Figure6.18.Isometricsectionviews.(a)Straightsection.(b)Halfsection.(c)Brokensection.(d)Offsetsection.

ISOMETRICASSEMBLYVIEWS

Two types of isometric assembly views are in common use, and they are theoutlineandexplodedisometricviews.Outlinepictorialviewsshowallexternalcomponents in mating positions as the example in Figure 6.19a. Explodedpictorialviewsshowallcomponentsinrelativepositionatsomedistanceapart,butalignedtoadjacentcomponents.Explodedassemblydrawingsaregreataidsin assembling, installations, andmaintenanceof products.They are popular incatalogs, maintenance manuals and guides, technical illustrations, and so on.Theyarenormallyarrangedalongisometricaxeswithcasesofseveraloffsetsifassembly is of a complexproduct.Figure6.19b shows the exploded isometricviewofFigure6.19a.

Figure6.19.Assemblyisometricviews.(a)Outline.(b)Exploded.

6.8

6.9

1.2.

3.

DIMETRICANDTRIMETRICPROJECTIONS

Dimetricandtrimetricprojectionsaresimilartoisometricprojection,butdifferintheanglesbetweenthereferenceaxesontheimageplane.Figure6.20showsexamples of isoplanes on cubes for dimetric and trimetric projections. Indiametricprojection, twoof theanglesbetween theprincipalaxesareequalasshowninFigure6.20a.Theseanglesarenormallygreaterthan90°,butlessthan180°.Theangle120°producesanisometricprojection,soitisnotacceptableindimetricprojection.Thethirdangleischosentobelessorgreaterthanthevalueof the equal angles.Commonvalues for angles indimetricprojection are15°,20°,25°,35°,and40°,withthehorizontallineatthebaseofthecube.Itismucheasier constructing isometric drawing than dimetric drawings. In trimetricprojection,theanglesbetweentheprincipalaxesaredifferentfromeachotherasindicatedfortheexampleinFigure6.20b.Thoughthisgivesgreaterflexibilityinthedrawingsthatmaybecreated,theconstructionprocessismoretediousthaneven that for diametric drawings. Thus, it is rare to find trimetric drawings.SomeCADpackages allowdimetric and trimetric views tobegenerated fromsolidmodels.However,isometricdrawingsarethefavorites.

Figure6.20.Examplesofisoplanesinotheraxonometricprojections.(a)Dimetric.(b)Trimetric.


Whatisanisometricprojection?What is the difference between an isometric projection and an isometricdrawing?Specifytherotationanglesinthehorizontalandverticalplanesforisometricprojection.

4.5.6.7.8.9.

10.11.

6.10

Listthetypesofisometricdrawingsyouknow.Defineisometricandnonisometriclines.Whatareisometriccircles?Namethetechniqueusedincreatingisometriccirclesinthischapter.Namethetwotechniquesusedinthischaptertocreateisometricdrawing.When would you prefer the centerline technique appropriate for isometricdrawings?Whatisaniso-detaildrawing?Listthetypesofisometricassemblydrawingscommonlyfound.

CHAPTEREXERCISES

Sketchtheisometricviewsshowninthefollowingfigures.Thelasttwofiguresareininchdimensions.


7.1

CHAPTER7

WORKINGDRAWINGS

INTRODUCTION

Aworkingdrawingisaspecialtypeofengineeringdrawingcreatedforuseasaproductionorconstructiondocument.Therefore,itisalsocalledaproductionorconstruction drawing. The design, manufacture, assembly, operation, andmaintenance of engineered products need proper documentation, and workingdrawings are the instruments used. They are employed for the technicaldocumentation and communication of design intent for simple to complexassemblies. Working drawings are fundamental in manufacturing andconstruction businesses and are considered to be legal documents. Quality,correctness, and completeness are paramount in their preparation. Due to theglobalization of the economy and technology and the increasingly growingpopularity ofmetric system inmost countries of theworld,working drawingsshouldbepreferablypreparedinmetricunits,especiallyinnewprojects.

Designed products usually consist of standard and nonstandard (custom)componentsorparts.Standardpartsaregenerallypurchasedfromvendors,whilecustompartsaremanufacturedin-houseorcontractedout.Eachnonstandardpartinanassemblyorsubassemblymusthaveadetaildrawing.However,standardparts in an assembly drawing do not need detail drawings, but properspecifications for each of them must be provided. Specifications are writteninstructions in working drawings, and they provide technical requirementinformation on parts, manufacturing, and assembling processes. They mayincludematerial typeandgrade,processingmethods,surfacefinish,andsoon.Specifications may appear as general notes or are put together as separatedocument. They should be clear and easy to understand. The design draftershouldaddspecificationstoaworkingdrawingasneeded,butthecorrectnessof

7.2

(a)(b)(c)(d)(e)(f)(g)(h)(i)(j)(k)(l)(m)(n)(o)(p)

7.2.1

thespecificationsistheresponsibilityofthedesignerorengineer.Practically,adesignprojectwillproduceseveraldrawings.Theseareusually

bundled together and delivered to a client as a set. A drawing set shouldcompletely communicate thedesign intent andconsistsofdetail and assemblydrawings.Detaildrawingsarepreparedoftenasmultiple2Dviewsdrawingsofasinglecomponentinonesheet.Havingmultipledetaildrawingsonasinglesheetis discouraged due to the changes that may occur in some components.Assembly drawings are prepared for mechanisms, units (subassemblies), andproducts.They show the relativepositionsof componentswhenassembled forfunctionaluse.Anassemblydrawingmust includeallparts inaproductwhichmustbelistedinabillofmaterials(BOM)orpartslist.

ELEMENTSOFWORKINGDRAWINGS

Working drawings consist of drawing views and annotations. Theymust havecompletedimensions,tolerances,andnotesforconstruction,manufacturing,andinspection.Theelementsusuallyfoundonaworkingdrawinginclude:

DrawingviewsTitleblockNameofpartorassemblyQuantityPartnumberMaterialandgradeDimensionsTolerancesScaleNotesDrawingnumberRevisionProjectnumberAssemblynumberZonemarkersSurfacequality

DRAWINGVIEWS

Thedrawingviewsinaworkingdrawingaretherequiredgraphicimagesofthe

7.2.2

product model. The drawing views depend on the type of documentationrequired, and annotation content will vary accordingly. The standard 2Dorthographicviewsarefront,top,andrightviewsinNorthAmericabasedon3rdangle projection. Auxiliary and sections views may be used to supplementstandardviewsformoredetailsandclarity.Figure7.1isanexampleofadetaildrawingconsistingofstandardtopandrightviews,sectionedfrontview,andanisometricinsert.

TITLEBLOCK

AtitleblockisprovidedinFigure7.1.Thetitleblockisusedtorecordimportantinformationaboutacompanyandapartorproduct. Itshouldcontainpertinentinformation likecompanynameandaddress,drawing title and recordnumber,sheet size and number, names of design drafter and checker, issue date, andprojectnumber.Otherinformationincludeapprovals,projectionstandard,scale,componentweight(estimateoractual)andCommercialandGovernmentEntity(CAGE) code (formerly Federal Supply Code for Manufacturers (FSCM)).Please refer to ANSI/ASME standard for title block dimensions. ByANSI/ASME standard, the title block should be located on the lower-rightcorner of the drawing sheet. However, some companies use their ownconvention.

Figure7.1.Aniso-insertinanortho-detaildrawing.

7.2.3

7.2.4

7.2.5

SCALE

Traditionally, a scale factor (SF) is required for each working drawing. Thedesign drafter chooses the scale of a drawing, which should be an integernumber,chosenfromasetofpreferredvalues.EnglishSFareoftenfractionsormultiplesof16.Commonvaluesare1,2,4,8,and16.CommonmetricSFsare1,2,5,and10.Forreductionscaling,thescalespecificationformatis1=SFforEnglishdrawingand1:SFformetricdrawing.ForinstanceifSFis2,thescaleisspecified in English as 1 = 2 and 1:2 in metric. For enlargement scaling inEnglishdrawings, the format isSF=1andSF:1 formetricdrawings.Note thattherearesomevariationsintheformatforspecifyingEnglishscales,especiallyinarchitecturaldrawings.Scale factorof1 implies full-scaledrawing ineitherEnglishormetricunit.

DIMENSIONSANDTOLERANCES

Working drawings must have functional sizes and associated tolerances formating components. Tolerances are allowed variations on dimensions and arecritical for proper functioning of some components. They are generally in theone-hundredthsandone-thousandthsofthefunctionalsizes.Standardtolerancesmay be added directly to the dimensions or specified in general notes, butcustom tolerances are added as local notes. Toleranced dimensions in detaildrawingsmaybeindicatedaslimitswithupperandlowervaluesorasfunctionalsizewithbilateralorunilateraltolerances.Thelimitspecificationiswellsuitedfor inspectionormeasurementpurposes.Components formassproductionandinterchangeable manufacture should have geometric tolerances added becausethey need close tolerances. Dimensions are generally not given in assemblydrawings, except for those critical for proper assembling. Please refer to theAppendicesformoreinformationontolerances.

SURFACEQUALITY

The surface quality of machined surfaces is often described by symbols androughnessvaluesindrawings.Themostpopularparameterofsurfaceroughnessisthearithmeticmeanaverage(Ra)value.Itistheresponsibilityofadesignerorengineertospecifyappropriatesurfacefinishforfunctionalityatminimumcost.Thesurfacetexturesymbolshouldbeplacedontheedgeviewofasurfacetobemachined. Please refer to the Appendix IV for more information on surface

7.2.6

7.2.7

quality.Notes:Notesprovidetextualinformationindrawings.Itisimportantthatall

relevant information about specific manufacturing requirements, such ashardness, strength, plating, polishing, shot peening, testing requirements andmethods, be specified in detail drawings as notes. Specific statements on heattreatment, general tolerances, surface finish, and so on, important for properfunctioning of components are included as notes. In fact all requirementsaffecting the manufacturing cost must be indicated so as not to infringe oncontractualagreementswithvendorsorthird-partysuppliers.Vendorscannotbeheld responsible for inferior goods if requirements are not made clear in acontract.Twotypesofnotesmaybefoundinworkingdrawings,namely,generalandlocalnotes.Generalnotesapplytothewholedrawingandareoftenlocatedat the base of a drawing ormay be part of the title block. Examples are “Alldimensions inmillimeters”; “Unspecified fillets and rounds=2.5mm”; “FAO(Finish all over)”; “For quotation purposes only”; “Top secret”; “Restricteddrawing”; “Do not copy”; “Confidential document”; and so on.References tostandardssuchastheAmericanNationalStandardsInstitute(ANSI),AmericanSociety for Mechanical Engineers (ASME), Military (MIL) can be made asgeneral notes.General instructionson assemblymethodsor proceduremaybeincluded in assembly drawings. Sometimes, general notes about welding,specifications on bolt tightening, and statements on cleaning and painting areadded to assemblydrawings.Localnotes applyonly to aportionor a specificfeature in a drawing.Please refer toFigure1.7 inChapter 1 for depictions ofleader line, callout, and balloon used for local notes. Specifications for screwfastenersareusuallyprovidedinlocalnotes.

ZONING

Zoning is a technique used in large sheet sizes to aid in quickly locatinginformation on a drawing. Please refer to Chapter 1 formore information onzoning.

PROJECTIONSTANDARD

There are two common standards for orthographic projection: first angle andthird angle. They are assigned standard symbols. A drawing should bear theappropriate projection symbol as in Figure 7.1. Symbols for 1st angle or 3rdangle are shown in Figure 7.2. Adhering to these standards is a professional

7.2.8

7.3

issue.

Figure7.2.Standardprojectionsymbols.

REVISIONBLOCK

ByANSIstandard,arevisionblockshouldbelocatedontheupper-rightcornerofthesheet,asshowninFigure7.1.Sometimes,itisplacedtotheleftoforontop of the title block. Changes to approved drawings are documented in therevisionblock.Thechangeinformationmayincludethenameofpersonmakingthe change request, description of change, reason for change, request date,changenumber,andapproval.Usually,conceptualandpreliminarydrawingsarenot approved drawings andmay be changedwithout proper documentation ofchanges. However, working drawings are approved drawings and changes onthemmustbeproperlydocumentedandapproved.

COMPONENTDETAILDRAWINGS

Detail drawings are required precise drawings for nonstandard parts in anassembly. They may be created from scratch or generated from a 3Dmodel.Chapters 2, 3, and 4 deal with the creation of standard and supplementary(auxiliaryandsection)orthographicviews.Afullyannotatedorthographicviewdrawing of a component may be referred to as ortho-detail drawing. It iscommoninpractice tohaveanisometric insertaddedtoortho-detaildrawings,as shown in Figure 7.1. An iso-insert aids visualization and is good forcompletenessofdocumentation.Afullydocumentedorthographicviewdrawingofanassemblyorunitmaybereferredtoasortho-assemblydrawing.

Figure 7.3a shows an isometric view of an object. Figure 7.3b is theEuropean standard orthographic representation, while Figure 7.3c is theAmerican standard orthographic representation. Proper alignment of drawingviews is paramount in detail drawings.All standard orthographic viewswhenshowntogetherinadrawingmusthavethesamescale.Isometricpictorialdetaildrawings(Iso-detaildrawings)areeasiertounderstand,butarenotstandardizedyet.Multiple isometric viewswould be themost practicalway to present iso-detaildrawings.

7.3.1

Figure7.3.Standardorthographicprojections.(a)Isometric.(b)Firstangleprojectionlayout.(c)Thirdangleprojectionlayout.

NECESSARYVIEWS

Detail drawings should be prepared with the minimum views required forcomplete description. Each component must be properly examined, and theminimumviewsnecessary for its representationdecidedon.A standardortho-detail drawing requires three orthographic views.However, some objectsmayneed less ormore views for complete description. For example, spheres needonly one view for representation. Components of simple shape (e.g., square,circular,triangular,andrectangular)orthathaverelativelycomplexprofiles,butuniformthickness(e.g.,sheetmetalcomponents)maybedescribedbyoneview.Suchdrawingsnormally includenotes specifying theobject thickness.Objectswithaxialsymmetryandwithoutcomplicatedfeaturesmayberepresentedwithtwo views. Examples are cylindrical, conical, and pyramidal objects. Irregularobjectsgenerallyneedtwoormoreviewsforrepresentation.

Sometimes,auxiliaryandsectionviewsarenecessaryindetaildrawings.Astheformofcomponentsgetsmorecomplicated,inclinedandobliquefacesmaybecomepartoftheirfeatures.Featuresonsuchsurfacesneedauxiliaryviewsforproper representation.A section view reveals internal or hidden features in anobject and is sometimes necessary for proper documentation of engineeredproducts.Bothpartandassemblysectionscanbecreated.Sectionandauxiliaryviewscansubstituteforstandardorthographicviews,andthishelpstokeepthenumberofviewsdown.Sectionviewsimprovevisualizationofdesigns,clarifymultiviews, and facilitatedimensioningofhidden features.Figure7.4 shows adetail drawing of a part that has a standard front view, two auxiliary views, apartial top view, and the isometric insert. It is obvious in this case that theisometricinserthelpsinvisualizingthecomponent.NoticethatarevisionblockisshowninFigure7.4.

7.4

(a)(b)(c)

7.5

Figure7.4.Mixedviewsdetaildrawing.

STANDARDPARTS

Traditionally, drawings of standard parts were omitted in detail drawings.However, in a solid model design, standard parts must be represented. Somevendorsmayprovidesolidmodeldatabasefortheirproductsandadesignercandownload them for use. If solid models of standard parts are unavailable,“dumb”models could be created. The dumbmodel lacks internal details, butbears external resemblance to the standard part.Dumbmodels can be createdusingboxandcylinderprimitivesandshouldsatisfythefollowingconditions:

haveaccuratesizeorvolumeofcomponent;haveapproximateoutlineorexternalfeatures;andhavenointernaldetails.

ASSEMBLYWORKINGDRAWINGS

Engineering products or systems may be decomposed into units (sub-assemblies), mechanisms, and components or parts. Drawings of completeproduct, unit, or mechanism are assembly drawings that constitute parts ofworking drawings. Assembly drawings show the relative positions of all thecomponents in a mechanism, unit, or product. They could be pictorial ororthographicinformconsistingofdrawingviewsandsometimesannotations.Inlargeorcomplexproducts,hundreds,ifnotthousands,ofunitsmaybeinvolved.

7.5.1

Such situations require the use of consistent unit assembly reference numbersthatarelinkedwiththeproductassembly.Itiscommonforamasterlistofalltheunits in the product to be compiled in a table. Similarly, a master list ofcomponents and the units they are needed in is compiled.Often, twoormoreunits may use the same component, and tracking the number of componentoccurrences in products from a company becomes important. Product datamanagement(PDM)softwareisdesignedtohandlesituationslikethis.Theyareable to monitor and generate reports on components and other relatedinformationonproductsonacompanywidebasis.

Theamountofannotationsinassemblydrawingsoftendependsonthenatureandcomplexityoftheproduct.Asarule,dimensionsarenotshowninassemblydrawingsbecausetheyaregivenindetaildrawings.Ifincluded,thedimensionsdefine relative positions of parts, not those of individual components.Overalldimensionsmaybe found in someassemblydrawings, and sometimes, criticaldimensions are indicated alongwithmanufacturing and assembly instructions.Otherassemblynotesmayincludebolttighteningrequirements,assemblywelds,cleaning, or decal for safety notices to be attached on product after assembly.Each assembly drawingmust include all standard and custom parts. It shouldincludeaBOMorpartslist,title,andrevisionblocks.

BOM

AssemblydrawingsnormallycarryablockforBOMorpartslist.Itisusuallyatable list of the parts or components in an assembly. Important information inBOMincludesitemreferencenumber,quantity,partname,partrecordnumber,description,catalognumber forstandardparts,andnameofvendors.The itemnumberisthenumberassignedtoacomponentinaparticularassemblydrawing,aformoflocalidentificationandcanchangewithdifferentassemblydrawings.The part number is a fixed number assigned to a specific component, by acompany.Itshouldnotchangefordifferentdrawingswithinthesamecompany.Because detail drawings are not required for standard parts, they must haveproperspecificationsprovidedinBOMorinaspecificationdocument.Standardparts are often mass-produced, and so, are usually cheaper to buy thannonstandard parts. Thus, maximizing the use of standard parts in a productdesignleads to lowerproductcostandfaster timeto themarket.Examplesarewashers,boltsandnuts,screws,bearings,pins,andsoon.Thespecificationsforstandard parts include name, size, grade, quantity, and catalog number. Ingeneral, other information like weight and stock size may be included in the

7.5.2

7.5.3

partslist.ByANSI/ASMEstandard,ablockforBOMshouldbelocatedonthelower-right corner of the drawing sheet on topof the title block, but variationexistsintheindustryonitsplacement.

TYPESOFASSEMBLYDRAWINGS

Assemblydrawingsmaybepresentedinorthographicorpictorialviews.Inthesetwo categories, many variants exist depending on the intended use. Commontypes of orthographic assembly drawings are outline and section drawings.Isometric pictorial views are the most common in design documentation.Popular types of isometric assembly views are outline, exploded, and section.Eachassemblydrawingisgivenauniquerecordnumber.

ISO-ASSEMBLYDRAWINGS

Isometric assembly drawings provide general graphic description of eachcomponentinoutline,exploded,andsectionviews.Outlinepictorialviewsshowall external components inmating position, as shown in Figure 7.5a. Internalcomponents are not shown in these views, so they provide only limitedinformation about a unit or product. Exploded pictorial views show allcomponents in relativepositionat somedistanceapart,butaligned toadjacentcomponents.Theyprovidevisualinformationaboutallthecomponentsinaunitorproductandaregreataidsinassembling,installations,andmaintenanceoftheproducts.Figure7.5b shows the exploded isometric view of the same productshowninFigure7.5a.AllthehiddencomponentsinFigure7.5aareexposedinFigure 7.5b. Sectioned isometric views show internal components in matingpositionat theplanedefinedbyacuttingplane line.Figure7.5cshowsahalf-sectionisometricassemblydrawingoftheproductinFigure7.5a.Theymaybebroken, half, or straight section drawings. Sectioned isometric views will, inmostcases,showalltheinformationthatexplodedisometricviewsprovide,buthavetheadditionalbenefitofbeingusefulforcheckinginterferencesofadjacentcomponents.Standardpartsandshaftsarenotsectioned,buttheyaredrawnwithall exterior features shown.Thin parts, like gaskets, are shown in solid black.Adjacentpartsarehatchedatdifferentanglesforclarityinsectionviews.

7.5.4

Figure7.5.Isometricassemblydrawings.(a)Outlineisometric.(b)Explodedisometric.(c)Halfsectionisometric.

Figure7.6.ExplodedisometricassemblywithBOM.

Acombinationofoutline,exploded,andsectionisometricviewsseemtobethe best for design documentation from a technical viewpoint. Interiorcomponentsnotrevealedintheoutlineorexplodedisometricviewwillshowinthe section view. The integrity of the fitting conditions of components can bejudgedfromthesectionview.Figure7.6showsanexplodedisometricassemblydrawingwithBOMandtitleblock,thoughnorevisionblockisincludedinthedrawingsheet.

ORTHO-ASSEMBLYDRAWINGS

Outline orthographic assembly views may be considered as modifiedorthographicdrawingswithremovedhiddenlines.Theycouldbestbedescribedasexteriororthographicdrawingswhenallhiddenlinesareremoved.Thus,theyprovide similar levelof informationasoutline isometricdrawings.Figure7.7ashows the outline ortho-view of Figure 7.7a. The hidden lines shown are for

clarity because it may be falsely assumed that all the components in theassemblyareallsolidswithoutthem.

Orthographic section assembly views, like isometric section drawings, areused for themanufacturing and assembly of complicated devices or products.Theymay be half or straight section drawings and provide virtually the sameinformation as isometric section or exploded drawings, butwithout the visualsimplicity of isometric views. In many situations, especially with simpleproducts, one full front section viewmay show all the parts in the assembly.Sometimes,a standardorthographic frontviewcombinedwithbrokensectionscan give a complete description of an assembly.Orthographic sections can beused to verify interference or clashes of adjacent components. Explodedisometricassemblyviewsarenotusefulinthisregard.Thesamehatchingrulesappliedtoisometricsectionviewsareusedinorthographicsectionviews.

Figure7.7.Sectionassemblydrawings.(a)Outlineortho-viewofassembly.(b)Frontortho-viewsection.

Modern computer design drafting (CDD) packages are becoming highlyautomated in drafting skills, especially in the drawing aspect. Orthographicviews of 3D models can be generated easily, and automatic dimensioning isprogressively being improved. As the capabilities of solid modeling softwareincrease, drafting skills will become common skills for technical personnel.Mostlikely,draftingskillsetwillfocusonannotations,reading,andinterpretingcomputer-generated drawings. Therefore, designers, architects, and engineerswill very likely be required to perform drafting tasks, especially in small andmid-sized companies. Consequently, print checking and reading will becomedominant skills for technology personnel because they will be required tointerpretandensurequalityassuranceofcomputer-generateddrawings.

7.6

7.6.1

•

•

•

•

••

CHECKINGDRAWINGS

Checking involves examining, comparing, and verifying model data andinformation. The accuracy of technical data cannot be overemphasized.Undetected errors carried into the manufacturing and assembly phases ofproductioncreateunnecessary expenditures that can tremendously increase theproduct price andmay kill the prospects of profitability. In small engineeringfirms, data checking is usually done by the designer or drafter, but in largecompanies, experienced design drafters called checkers do the checking orexperiencedengineersspendagoodpartoftheirworktimecheckingmodelanddrawing data. Normally, the drafter does the first check, then; the designerreviewsthedataforfunctionality,practicability,economy,manufacturability,andsoon.Corrections,ifneeded,aredonebytheoriginaldrafter.Thefinalchecker(engineer or supervisor) is expected to discover any remaining error(s). To beeffective,checkingshouldbedonesystematically.

ASSEMBLYDRAWINGCHECKLIST

InaCDDenvironment, the solidmodelsofallcustom(nonstandard)partsarecreatedinadatabase.Eachunitassemblyisnormallyinaseparatefile,andthefinalproductassemblymodel is themasterproduct file.Eachassemblymodelshouldbecheckedforinterferencesandcorrected.Animationandsimulationofmechanismsandassembliesaregreattechniquesusedinverifyingfunctionalityand checking interferences. If the software for these techniques are available,they should be employed for integrity checking. The following points arenoteworthy:

Check product and unit assembles for serviceability, economy, assembling,repair,lubrication,andsoon.Check that all assembly and unit (subassembly) drawings have parts list orBOM.Traditionally, main castings or forgings are listed first, followed by partsmanufacturedfrommaterialstocks,andlastly,standardparts.However,seriallistingmakesforbetterclarityandreadability.Check for soundness of part design with respect to strength, material,manufacturability,andsoon.Checkthatfitsareeconomicalandpracticalformatingparts.Checkmovingpartsinallpossiblepositionsandensureclearancesareproper

•••

7.6.2

1.2.3.

4.5.••••

6.7.

1.2.3.4.5.6.7.8.

forfunctionality.Checkforclashesofallmatingpartsinanassembly.Checkthatallcustompartshavemodelsanddrawings.Checkthatallstandard(purchase)partsarelistedandcorrectlyspecified.

DETAILDRAWINGCHECKLIST

Afterthemasterproductfileandunitassemblyfileshavebeencreated,thedetaildrawing of each part is prepared. Checking of all part models and detaildrawingsshouldbedonetoensureaccuracyandcompleteness.Readabilityisofprimeimportanceindrawingpreparation,andneatnessistakenforgranted.Thefollowingmayhelpasachecklist.

DrawingViews

Establishrequiredviewtypes(standard,auxiliary,section,isometric).Placeviewsbyprojectionstandard(3rdor1stangleprojection).Ensureproperspacingofviews,avoidovercrowding,andaimforabalancedlayout.Ensureproperalignmentofviews.Usetherightlinestylesandappropriatelineweightorthickness:Ensurethatallvisiblelinesareshown.Ensurethatallhiddenlinesareshown.Ensurethatallcenterlinesareshown.Ensurethatallobjectsareinappropriatelayers.

Usethesamescaleforallstandardviews.Provide local scale for iso-insert, auxiliary, and section views wherenecessary.

Annotations

Establishtextfontandheightandsettextcolortoblackforbestcontrast.Makesureallextensionlinesgototherightfeature.Makesurearrowheadsendattherightextensionlinesorfeatures.Ensurecorrectnessandproperdimensionplacement.Correctambiguityandillegibilityofdimensions.Overallorprincipaldimensionsshouldbeshown.Makesurethatthereisnorepetitionoromissionsofdimensionsforfeatures.Ensureproperandeconomicaltolerances(generalandgeometric).

9.10.11.12.13.14.15.

1.2.3.4.

1.

2.

3.

4.

5.6.

7.7

Ensureproperandeconomicalsurfacefinish.Ensureproperandeconomicvaluesoffilletsandrounds.Makesurescrewthreadspecificationsarecorrect.Makesurelocalandgeneralnotesarecorrect.Checkthatnotesareinproperorderandlogicallyplaced.Checkthatthespecifiedmaterialisproperandeconomical.Checkthatthespecifiedmanufacturingprocessisproperandeconomical.

Administrative

Providetitleblockandpertinentinformation.Providerevisionblockandinformation.Ensurecorrectnessofinformationintitleandrevisionblocks.Ensuredraftingstandardsareusedappropriately.

CheckPrints

Acheckprintisahardorpapercopyofadrawingthatisgeneratedforthepurposeofreviewing,checkingandcorrectinganyerrorinthedrawing.As humans, we are prone to errors and oversight; review is absolutelynecessaryindesigndrafting.Drawingerrorscanbediscoveredandeliminatedbysystematicandcarefulchecking.Always print a hard copy of a CDD drawing on the appropriate standardsheet.Carefullyreviewtheprintedcopyandnoteallerrorsforcorrection.Ensurethatallidentifiederrorsarecorrected.

Knowledge, thoroughness, and good judgment are vital for catchingmodelanddrawingerrors.Drawingscalemaybeindicatedinworkingdrawings.Theycan be selected using scale factor models that provide tools for trainingdesigners,drafters,architects,andengineers,aswellashelpinplanningdesigndocumentations. Never accept or approve a dimensioned drawing without athoroughcheckofthedimensionsandlayoutofviews.Allerrorsidentifiedmustbecorrectedbeforereleasingthedrawing.

SPECIFICATIONDOCUMENTS

Specificationsdealwithexplanatoryorrequiredinformationneededondrawings

7.8

for proper interpretation or clarification of certain requirements. In suchsituations, theinformationisput together inaspecificationdocument.Insomedesign discipline (e.g., architecture), specification documents are required asseparate information. Sometimes, all the technical information for a designprojectcannotbeplacedinthedetailandassemblydrawings.Codes,standards,andregulationsmustbeadheredtoinspecificationdocuments.Testingstandardsandprocedures,qualitycontrol,surfacetexture,packagingrequirements,andsoon often come in specification documents. Large and complicated designprojects, such as commercial buildings, process plants, and heavy equipment,mayneedmanypages of specifications for construction, assembly, packaging,shipping, erectionor installation, and storageconditions.Specifications shouldbeclear,concise,andcomplete,andcriticalinformationshouldbehighlighted.

WORKINGDRAWINGSET

Most design projects produce several drawings that are put together anddeliveredtoaclientasaset.Aworkingdrawingsetisapackageofallthedetaildrawings, assemblydrawings, and specificationdocuments, if any, in adesignproject. As mentioned in the introduction section, a drawing set shouldcompletelycommunicatethedesignintent.Abuilderofadesignshouldbeableto construct the artifact by correctly interpreting the drawings and faithfullyfollowingthespecificationsinthedrawingset.SomeCDDpackagesareabletogenerateadrawingsetforaproject.Thedesignofficeusuallykeepsacopyofadrawingsetinvaultsorfireproofcabinets.Backuporarchivalelectroniccopiesof drawing sets are kept in CDD offices. An example of a drawing set ispresented next for a unit of 14 components. An outline isometric view andexplodedisometricviewarepresentedinthesamedrawingwithBOMinFigure7.8.Sixofthecomponentsarecustomparts,sotherearesixdetaildrawingsinthesetandareshowninFigure7.8toFigure7.14.TheremainingeightstandardpartsarepresentedinasinglesheetinFigure7.15withtheirspecificationsinatable.Thetableiscalledapurchaseschedulehere.Standardpartsmaybefoundinvendor’scatalogs,Machinery’sHandbook,Fastener’sHandbook,andsoon.Please refer to the Appendix I for more information on screw fasteners. Inaddition to screw fasteners, information on general tolerancing, geometrictolerancing,andsurfacequalityareprovidedintheAppendices.It is,however,emphasized that theavailable information in theAppendices is introductory innatureduetospaceconsiderations.Readersareadvisedtodofurtherresearchonthesesubjectsandrefertorelevantstandards.

Figure7.8.Explodedassemblydrawing.

Figure7.9.Shaftdetaildrawing.

Figure7.10.Flangedetaildrawing.

Figure7.11.Pulleydetaildrawing.

Figure7.12.Geardetaildrawing.

Figure7.13.Retainerdetaildrawing.

7.9

1.2.3.4.5.

Figure7.14.Sleevedetaildrawing.

Figure7.15.Scheduleofpurchaseparts.


Whatisaworkingdrawing?Howimportantisaworkingdrawing?Whatfactorsguidethepreparingofworkingdrawings?Whenareworkingdrawingsrequired?Namethetwofundamentaltypesofworkingdrawings.

6.7.8.9.10.11.12.

7.10

Brieflycompareandcontrastdetailandassemblydrawings.Namethecommontypesofdetaildrawings.Namethecommontypesofassemblydrawings.Sketchthesymbolsfor1stand3rdangleprojections.WhatisBOM?Whichtypeofdrawingisitusuallyassociatedwith?Whatisaspecification?Whyisitnecessary?Whatisadrawingset?Whichdocumentsareincludedinadrawingset?

CHAPTEREXERCISES

Prepare adrawing set for thedevices shownas follows.Theoutline isometricview should be the first drawing, followed by the exploded isometric viewdrawing.Thecomponentdrawingshouldbearrangedbytheitemnumber.

FigureP7.1.ComponentdrawingsofFigureP7.1.

FigureP7.2.ComponentdrawingsforFigureP7.2a.

FigureP7.3.ComponentdrawingsforFigureP7.3a.

A1.1

A1.2

APPENDIXI

SCREWFASTENERS

SCREWFEATURES

Amechanicalscrewisacylinderorconethathasahelicalridgecalledathread;hence,screwsarethreadedcomponents.Ahelixhasoneormoreturns,therefore,ascrewcanhaveseveralturns.Ifthehelixisontheoutsidesurfaceofacylinderoracone,itisanexternalthread.Ifthehelixisontheinsidesurfaceofahollowcylinder or cone, it is an internal thread. There are two types of mechanicalscrews,namely,screwfastenersandpowerscrews.Screwfastenersareusedtohold twoormorecomponents together inadetachable joint.PowerscrewsaredesignedtotransmitpowerandormotionbutarenotdiscussedinthisAppendix.The endsof external threads are normally chamfered at 45° for easier startingand engagement. FigureA1.1 shows the elements of an external and internalthreadform.

STANDARDTHREADSANDTHREADPROFILES

Screw threads have been standardized nationally and internationally. TheInternational Standardization Organization (ISO) thread standard is themetricthread.Therootofmetricscrewscanbeflatorrounded.FlatrootprofilescrewsareidentifiedbytheletterM,whileroundedrootprofilescrewsareidentifiedbylettersMJ.TheMprofilethreadisforgeneralapplications,whiletheMJprofileispreferred inhigh-fatigue stress environment.Thenational thread standard isthe Unified National (UN) thread in the United States. It will be called theEnglishthreadinourdiscussions.

A1.3

A1.4

FigureA1.1.Threadnomenclature.(a)Externalthread.(b)Internalthread.

THREADSERIES

Threadseriesarebasedon the typeofpitch.Themetric threadhas twoseries,namely,coarseandfinepitchseries.Forthesamemajordiametersize,thefinepitch series hasmore threads or smaller pitches. The English thread has fourseries: coarse (UNC), fine (UNF), extra fine (UNEF), and constant pitch.English threads are characterized by threads per inch (TPI), the reciprocal ofpitch.ThecoarseserieshastheleastTPI,whiletheextra-fineserieshasthemostTPI. In the constantpitch series, differentmajordiameter sizeshave the samepitchorTPI.

THREADCLASSES

Athreadclassoffitdeterminesthemanufacturingprecisionofthethread.TableA1.1showstheclassesofthreadsinthemetricsystem,whileTableA1.2showstheclassesofthreadsintheEnglishsystem.

TableA1.1.Metricthreadclasses

Fitclasses

Fitname Internalthreads Externalthreads Applications

Free 7H 8g Forquickandeasyassembly

Medium 6H 6g Forgeneralengineeringapplications

Close 5H 4g Forprecisionapplications

TableA1.2.Englishthreadclasses

A1.5

Classname Applications

Class1 Forquickassemblyandwhenplayisacceptable

Class2 Forgeneral-purposeapplicationsandforthreadsofmassproduction

Class3 Forprecisiontools,high-stressandvibrationapplications

THREADSPECIFICATION

A thread specification provides necessary information about the thread formanufactureorpurchase.Threadsmaybespecifiedinbasicordetailedformat.FigureA1.2ashowsabasicspecificationofametricthread,whileFigureA1.2bshowsadetailspecification.FiguresA1.3aandA1.3bshowthebasicanddetailspecificationofthreads,respectively,intheEnglishunits.TableA1.3gives theinterpretationsof the threadelements shown inFigureA1.2,whileTableA1.4gives the interpretation of the thread specification elements shown in FigureA1.3.TheTPIelementofEnglishthreadisthereciprocalofthethreadpitch.

FigureA1.2.Metricthreadspecifications.

TableA1.3.Interpretingmetricthreadspecification

Item Description

1 Metricthreadidentifier

2 Majordiameter(mm)

3 Separator

4 Pitch(mm)

5 Majordiametertolerancespecification

6 Minordiametertolerancespecification

FigureA1.3.Englishthreadspecifications.

TableA1.4.InterpretingEnglishthreadspecification

Item Description

1 Majordiameterornumberreference

2 TPI

3 UN

4 Coarse(seriesidentifier)

5 Class

6 A:externalthreadandB:internalthread

7 LH:left-handthread;RH:right-handthread

8 Numberofstarts

9 Separator

10 Lengthvalue

11 Lengthidentifier

APPENDIXII

GENERALTOLERANCINGANDDIMENSIONING

There are two types of tolerances, namely: General and geometric tolerances.General tolerance is used to control the size of linear and angular features.General linear tolerances are about two to three orders ofmagnitudes smallerthanthelineardimensions.Theyareestablishedfrombasicsizesandtolerancegrades.Linearsizesincludelength,width,breadth,height,depth,thickness,arclength, diameter, and radius. Angular tolerance is used to control angulardimension.Generaltolerancesarespecifiedbasedonthefunctionalrequirementsfor manufactured items. They are usually selected from national and orinternational standards. The commonly used international standard is theInternationalTolerance(IT)Grade,definedinISO286.Thisgradeidentifies18tolerancegradesofrelativeaccuracythatmanufacturingprocessescanproducefor a given dimension. Grades are designated as IT01 to IT16, with smallernumbersrepresentingtightertolerances.Tolerancesaremeasuredinmicrometers[µm]inmetricunitsandmicroinches[µin]inEnglishunits.Formeasuringtools,grades01,0,and1to8arerecommended.Forcomponentsmadefrommetals,grades7to15arerecommended.Forlargemanufacturingtolerances,grades11to16maybeused.Sizelimitsofitemsdependonboththetolerancegradeandthefundamentaldeviation.Thefundamentaldeviationclassdefinestherelativepositionoftheupper-orlower-limitsizeofanitemfromatheoreticalreferencesize called the basic or preferably design size. The classes are designated bylettersandsymbols.ThefundamentaldeviationclassesforholesareA,B,C,D,E,F,G,H,JS,J,K,L,M,N,P,R,S,T,U,V,X,Y,Z,ZA,ZB,andZC.Therestof the letters, that is, I, L, O, Q, andW, are not used. For shafts, the samesymbolsareused,butinlower-caseletters.ForholesclassesAtoH,thelower

A2.1

A2.2

deviationisabovethebasicsize,withthelowerdeviationforHclassbeingzero.ForholeshavingsymbolsJtoZC,thefundamentaldeviationisbelowthebasicsize. Practically, the lower deviation for holes A to H is the fundamentaldeviation, and for holes J to ZC, the fundamental deviation is the upperdeviation.Thefundamentaldeviationsforshaftsareoppositetothoseofholes.Thatis,forshaftsatoh,theupperdeviationisbelowthebasicsizeandhavingthe upper deviation being zero for shaft h. Then, for shafts having symbol inbetweenjandzc,itisabovethebasicsize.Thefundamentaldeviationforshaftsatohistheupperdeviation,andforshaftsjtozc,itislowerdeviation.Pleaserefer to ANSI B4.2 and B4.4M for details. Tables are available in thesedocumentswithtolerancesofsizelimitsbasedontolerancegradesandpreferredsize ranges.There are twobasicways that general tolerancemaybe specifiedandthesearewithsymbolsorvalues.

SYMBOLICSPECIFICATION

Insymbolicspecification,thedesignsizeandtolerancegradeareindicated.Forinstance, 40H8 is a symbolic specification of tolerance on a size. In thisexample, 40mm is thedesignor functional size,H identifies the fundamentaldeviationclass,and8 is the international tolerancegrade.Theenduserof thisspecificationwouldhave todetermine the size limits for thedesign sizeof40mm.Inthisexample,thelimitformatfor40H8is40.039/40.000,where40.039mmis themaximumsize(upper limit)and40.000is theminimumsize(lowerlimit)permittedbyH8tolerancespecification.

VALUESPECIFICATION

In value specification, the size range or limits are indicated. The size rangespecificationgivesthefunctionalsizeandthedeviationsaroundit.Twoformatsfor size range specification are in use, namely: Unilateral and bilateral. Inunilateralspecification,thetotalvalueofthetoleranceisappliedtoonesideofthedesignsize,asshowninFigureA2.1.Bilateraltolerancecouldbeofequalorunequaldeviationsrelativetothedesignsize.FigureA2.2showsanexampleofequalbilateralspecifications.Thelimitspecificationformatgivestheupper-andlower-limit values of size, as shown in FigureA2.3. The usual practice is toindicate value specification on working drawings and symbols on assemblydrawings. The limits format of value specification is more directly related to

A2.3

measurementandinspectionandshouldbepreferred.

FigureA2.1.Unilateraltolerancespecification.

FigureA2.2.Bilateraltolerancespecification.

FigureA2.3.Limitsspecification.

HOLE-BASISORSHAFT-BASISFITSYSTEMS

An assembly fit is created by combining the tolerances of mating parts anddeterminestherelativeclearanceorinterferencebetweentheparts.Afitmustbechosenverycarefullyinordertoensurefunctionalityofanassembly.Thetypeof device and its applications are important factors in determining a fit.Now,several combinations of shaft andhole sizes are possible in defining a fit. So,standardization is an economic advantage because it reduces variety andsimplifies design choices. National (ANSI/ ASME) and international standard(ISO) fits have been developed based on hole- and shaft-basis. It is better toselecthole-basisfitbecauseitiseasiertoproduceshaftstotherequiredsizeon

this basis.A hole-basis system uses the design size of hole as a reference fortolerancedisposition,whileashaft-basissystemusesthedesignsizeofshaftasareference. Hole-basis is used when a shaft component has variable cross-sectional sizesalong its lengthorholecomponenthasaconstant cross-sectionalongitslength.However,theshaft-basissystemisverygoodformanufacturingbright drawn bars. Shaft-basis is used when a shaft component has constantcross-sectional size along its length or hole component has variable cross-sectional sizes along its length. Tables of preferred tolerances and fits areavailable,sodesignersneednotcalculatetolerancesandfitsfromscratch.TableA2.1showstherecommendedmetricpreferredfitsforgeneralapplications.

TableA2.1.Preferredfits(ANSIB4.2)

ISOsymbol

Holebasis Shaftbasis Fittype Application

H11c11 C11h11 Looserunning

Forwidecommercialtoleranceorallowancesonexternalcomponents.

H9d9 D9h9 Freerunning Goodforlargetemperaturevariations,highrunningspeeds,orheavyjournalpressures.Notwhenaccuracyisimportant.

H8f7 F8h7 Closerunning Forrunningaccuratemachinesandforaccuratelocationtomoderatespeedsandjournalpressures.

H7g6 G7h6 Sliding Forfreelinearandturningmovement,accuratelocation,butnotforfreerunning.

H7h6 H7h6 Snug Forlocatingstationarypartswhereassemblyanddisassemblycanbefreelydone.

H7k6 K7h6 Locationaltransition

Foraccuratelocation.Clearanceorinterferenceislikely.

H7n6 N7h6 Locationaltransition

Forgreaterinterferencewheremoreaccuratelocationisdesired.

H7p6 P7h6 Push Forrigidandproperalignmentofpartsandwhereaccuracyinlocationisaprimefactor.Nospecialborepressureinassembly.Theholebasisiscommonlyusedfortransitionfitforbasicsizesintherangeof0to3mm.

H7s6 S7h6 Drive Forordinarysteelpartsorshrinkfitsonlightsections.Thetightestfitforcastironparts.

H7u6 U7h6 Force Forpartsthatcanresisthighstressesorshrinkfitswhereheavypressingforcesrequiredareimpractical.

APPENDIXIII

GEOMETRICTOLERANCINGANDDIMENSIONING

Geometric dimensioning and tolerancing (GD&T) is an accurate technique fordefiningandcontrollingtheformsandshapesoffeatures.Itsuniqueapproachindimensioning is the independent specification of the size and geometrictolerances. It combines general and geometric tolerances in a feature controlframe.Geometric tolerance types include straightness, flatness, circularity, andcylindricity, and orientations of shapes such as angularity, parallelism, andperpendicularity. Run-out relates to radial features and reference axis andfeaturesthatare90o toareferenceaxis.TableA3.1shows thecommonlyusedgeometric tolerancing symbols that are adopted internationally. Figure A3.1showsexamplesofGD&T.

TableA3.1.GD&Tsymbols

FigureA3.1.ExamplesofGD&T.

A4.1

APPENDIXIV

SURFACETEXTURE

Surfacetextureisusedtodescribeseveralelementsofamachinedsurface.Themajor elementsof surface texture are roughness,waviness, lays, and flaws, asshowninFigureA4.1. Surface roughness is the tiny irregularities on surfaces,usually of the order of microns. Surface waviness describes a more regularfeature of valleys and crests on a surface, usually of the order ofmillimeters.Surfaceroughnessissuperimposedonsurfacewaviness.Layisusedtodescribethe direction of the predominant surface pattern. Flaw describes anyrecognizable defect on a surface. Surface texture is generally specified withsymbols,asshowninFigureA4.2.Severalparametersofsurfaceroughnesshavebeen defined, but the most popular is the arithmetic mean average surfaceroughness height value (Ra). It is in microns (SI units) or is measured inmicroinches (English units).The control of surface roughness is important fortwo reasons, namely: To reduce friction and control wear. These two factorsinfluence the service lifeandperformancequalityofmachinesandequipment.Theaccuracyofmeasurementsisrelatedtotheaccuracyofthesurfacebecausefineresolutioncannotbedetectedonafreehandsurface.Itistheresponsibilityofadesignertospecifyappropriatesurfacefinishforfunctionalityatminimumcost.ANSIB46.1dealswithsurfacecontrol,andsymbolsofsurfacetexturearedefinedinANSIY14.36.

SURFACETEXTURESPECIFICATION

Surface texturemaybe specified in threeways, namely, full, basic, or generalspecification. In the full and basic specifications, the surface texture symbolshouldbeplacedperpendicular to theedgeviewof thesurface,as indicatedin

A4.1.1

A4.1.2

FigureA4.2andFigureA4.3.

FigureA4.1.Elementsofsurfacetexture.

FigureA4.2.Fullspecificationofsurfacetexture.

FigureA4.3.Basicspecificationofsurfacetexturesymbol.

FULLSPECIFICATION

In full specification, parameters of surface texture are indicatedon the texturesymbol for the referenced surface. Figure A4.2 shows a full specification ofsurface texture. The labeling is only for understanding; this is not part of aspecification.

BASICSPECIFICATION

Only important parameters of surface textures are indicated on the texture

A4.1.3

A4.2

symbol for the referenced surface. How many parameters are consideredimportantdependsonthedesignerorengineer.Inmanysituations,themaximumroughness height is all that is indicated in a basic specification, as shown inFigureA4.3 (a) and FigureA4.3 (b).When themaximum roughness value isindicatedonatexturesymbol,itimpliesthatanyvaluesmallerthanthatshownisacceptable.

GENERALSPECIFICATION

Parameters of surface textures are not indicated on the texture symbol for thereferencedsurface.Thesurfacetexturesymbolandanoteareaddedtodrawing.AnotesuchasFAO(finishallover)iscommon.FigureA4.3(c)isanexampleof a general specification. Figure A4.4 is an example of a component withsurfacefinishspecification.

SURFACEROUGHNESSPRODUCTION

Different manufacturing processes have different capabilities for producingsurfacetexturequality.Generally,machiningwithheavyfeedsandslowspeedsresultsinfreehandsurfacesorhighroughnessvalues.Machiningwithfinefeedsandhighspeedsgivessmoothsurfacesorlowroughnessvalues.Often,afinishmachiningprocessiscarriedoutafterafreehandmachiningprocessinordertoachieve a desired surface finish. Table A4.1 summarizes typical roughnessheight values for some manufacturing processes. Higher or lower roughnessvaluesmaybeobtainedunderspecialconditions.

FigureA4.4.Applicationexample.

TableA4.1.Typicalsurfaceroughnessheightforsomemanufacturingprocesses

Roughnessheight,Ra(µm) ManufacturingProcess(es)

12.5–1.6 Planning,shaping

6.3–1.6 Drilling,milling

6.3–0.4 Boring,turning

3.2–0.8 Broaching,Reaming

1.6–0.1 Grinding

0.8–0.1 Honing

0.4–0.1 Lapping

0.2–0.25 Superfinishing

BIBLIOGRAPHY

Bertoline,G.R.,E.N.Wiebe,C.L.Miller,andJ.L.Mohler.1997.TechnicalGraphicsCommunication,2nded.WCBMcGraw-Hill.

Duggai,V.2000.CADDPrimer.NewYork,NY:MailmaxPublishing.Earle,J.H.1991.DraftingTechnology,2nded.Reading,Addison-WesleyPublishing.Giesecke,F.E.,A.Mitchell,H.C.Spencer,I.L.Hill,J.T.Dygdon,andJ.E.Novak.2002.TechnicalDrawing,

12thed.UpperSaddleRiver:PrenticeHall.Jacobs,G.E.2008.IPT’sGuidetoBlueprintInterpretation,3rded.Edmonton:IPTPublishingandTraining

Co.Jefferis, A., and D.A. Madsen. 2005. Architectural Drafting and Design, 5th ed. Thomson Delmar

Learning.Jensen,C.,J.D.Helsel,andD.Short.1996.EngineeringDrawingandDesign,5thed.Glencoe.Kicklighter,C.E.,andW.C.Brown.2008.DraftingandDesign,7thed.Goodheart-WilcoxCo.Lieu,D.K.,andS.Sorby.2009.AnIntroductiontoVisualization,Modeling,andGraphicsforEngineering

Design.DelmarCENGAGELearning.Mabrey,R.L.1998.EngineeringGraphics:Principles,StandardsandModels.AddisonWesley.Madsen,D.A.,T.M.Shumaker,J.L.Turpin,andC.Stark.1996.EngineeringDrawingandDesign,2nded.

NewYork,NY:Delmar.Madsen,D.A., J.Folkestad,K.A.Schertz,T.M.Shumaker,C.Stark, and J.L.Turpin.2002.Engineering

DrawingandDesign,3rded.NewYork,NY:DelmarThomsonLearning.Madsen,D.A.2017.EngineeringDrawingandDesign,6thed.CengageLearning.Meyers, D.F., F.M. Croft, Jr., M.J. Miller, J.T. Demel, and H.L. Enders. 2007. Technical Graphics.

Missions,SDCPublications.Nee,J.G.1983.MechanicalEngineeringTechnology:ProductDesignandDraftingProblems.AnnArbor:

PrakkenPublications.Pond,R.J.1999.IntroductiontoEngineeringTechnology,4thed.UpperSaddleRiver:PrenticeHall.Schwartz,M.2004.BasicEngineeringforBuilders.Carlsbad:CraftmanBookCompany.Sexton,T.J.2006.EngineeringGraphics:TheoryandProblems.Missions,SDCPublications.Shih,R.H.2004.AutoCAD2005Tutorial:3DModeling.Missions,SDCPublications.Shih,R.H.2006.ParametricModelingwithUGSNX4.Missions,SDCPublications.Standiford,K.,andD.Standiford.2001.DescriptiveGeometry:AnIntegratedApproachUsingAutoCAD.

Delmar.Tickoo,S.2012.SolidEdgeST4.CADCIMTechnologies.Tickoo,S.1998.AutoCAD:AProblemSolvingApproach.AutoDeskPress.

ABOUTTHEAUTHOR

DrEdwardE.OsakueiscurrentlyanAssociateProfessorintheDepartmentofIndustrialTechnologyatTexasSouthernUniversity,Houston,Texas.Heearnedhis bachelor’s andmaster’s degrees, both inProductionEngineering, from theUniversity ofBenin,BeninCity,Nigeria.He obtained his PhD inMechanicalEngineering from the University of New Brunswick, Fredericton, Canada. DrOsakuewastheeducationsupervisor/chairoftheschoolofdraftinganddesignfrom1999to2006at ITTTechnical Institute,HoustonSouth.Hehasauthoredandco-authoredseveraltechnicalpapersinengineeringdesignanddrafting.DrOsakueisaregularpresenteratnationalandinternationaltechnicalconferencessuchAmericanSocietyofMechanicalEngineers(ASME)andAmericanSocietyfor Engineering Education (ASEE). He is also an Adjunct Faculty ofEngineeringDraftingandDesignDepartment atHoustonCommunityCollege,Houston,Texasthenation’slargestcommunitycollege.

INDEX

AActualsize,90Alignedsectionviews,75AmericanNationalStandardsInstitute(ANSI),2AmericanSocietyforTestingMetals(ASTM),3Annotationsindrafting,10–14isometric,129–130

ANSI.SeeAmericanNationalStandardsInstituteArcsandcirclesdimensioning,95–96isometricdrawings,120–123

Assemblydrawingchecklist,151Assemblysectionviews,79AssemblyworkingdrawingsBOM,147iso-assemblydrawings,148–149ortho-assemblydrawings,149–150overviewof,146–147typesof,148

ASTM.SeeAmericanSocietyforTestingMetalsAuxiliarydrawingviewscombinedstandardandpartial,61–62constructingoninclinedfaces,50–52constructingonobliquefaces,52–56fullandpartial,48–49generatingforinclinedfaces,57–58generatingforobliquefaces,59–61overviewof,45understandingof,45–47viewimagebox,48visualizing,48–49

Auxiliarysectionviews,77–78Auxiliaryviewimagebox,48Axonometricprojections,22

BBasicsurfacetexturespecification,183Billofmaterials(BOM),9BOM.SeeBillofmaterialsBondstationary,5Boundingboxconcept,25–26Boxtechnique,123–124Breaklines,16–17Brokensectionviews,76

CCenterlines,16Centerlinetechnique,128–129Chamferdimensioning,98–99Checkingdrawingsassemblydrawingchecklist,151detaildrawingchecklist,152–153overviewof,150–151

Componentdetaildrawings,144–146Conventionalbreaklines,81Counterbore,99Countersink,99Cuttingplanelines,16Cuttingplanelinestyles,69

DDesignsize,90Detaildrawingchecklist,152–153Detailsectionviews,77Dimensionalstability,5Dimensioningangles,96arcsandcircles,95–96CDDautomaticdimensionplacement,108–111chamfer,98–99counterbore,countersink,andspotface,99definitionof,89elementsandsymbols,91–92filletandround,97–98holes,96–97keyseatsandkeyways,99–101manual,105–108methodsof,102–104necksandundercuts,101placing,94–102repeatedfeatures,101–102slots,97

style,104–105typesandlinespacing,92–94

Dimensionlines,16Dimensionsandtolerances,142Dimetricprojections,133–134Drafting,1Draughting,1Drawingmediadrawingsheetorpapersizes,6overviewof,5–6sheetorientation,6–7

Drawingsheet,6Drawingunitsofangle,4–5oflength,4

Drawingviews,140–141principaldimensionsandlayout,30–31principalviews,27–28projectionstandards,28–30standardviews,30

Durability,5

EEngineeringdiagrams,89Engineeringdrawingsdefinitionof,89dimensionsin,90

Eraseability,5Extensionlines,16

FFilletandround,dimensioning,97–98Fullauxiliaryview,48–49Fullsectionviews,72Fullsurfacetexturespecification,182

GGD&T.SeeGeometricdimensioningandtolerancingGeneralsurfacetexturespecification,183Geometricdimensioningandtolerancing(GD&T),177–179Ghosting,5Gridpapers,6

HHalfsectionviews,76Hatchpatterns,69–71Hiddenlines,15–16

Hole-basisfitsystem,173–174

IIEEE.SeeInstituteofElectricalandElectronicEngineersInclinedfacesconstructing,50–52generatingforauxiliarydrawingviews,57–58isometricdrawings,124–125

InstituteofElectricalandElectronicEngineers(IEEE),3InternationalStandardizationOrganization(ISO),2Irregularcurves,isometricdrawings,127ISO.SeeInternationalStandardizationOrganizationIso-assemblydrawings,148–149Iso-detaildrawings,130–131Isometricannotations,129–130Isometricassemblyviews,132–133Isometricdrawingsannotations,129–130applicationsof,130–133boxtechnique,123–124centerlinetechnique,128–129constructingarcsandcircles,120–123definitionof,117dimetricandtrimetricprojections,133–134explodedviews,131–132objectwithangledfaces,125–126objectwithellipseoninclinedfaces,126–127objectwithinclinedfaces,124–125objectwithirregularcurves,127objectwithnormalfaces,124objectwithobliquefaces,125projectionandscale,117–119typesof,119–120

KKeyseatsandkeyways,99–101

LLetteringconventions,10–14Linespacing,92–94Linestylesapplying,17–18precedenceof,17typesof,14–17

MManualdimensioning,105–108

Multiviewdrawingchecklistfor,39standard,33–37

Mylar,5

NNecessaryviews,145–146Necksandundercuts,101Nonuniqueviews,31

OObjectplanes,24–25Obliquefacesconstructing,52–56generatingforauxiliarydrawingviews,59–61isometricdrawings,125

Offsetsectionviews,73Ortho-assemblydrawings,149–150Orthographicprojectionassumptions,24concepts,23definition,23

Orthographicviewprojection,26–27

PPapersizes,6Parallelprojection,22Partialauxiliaryview,48–49Partialsectionviews,76Perspectiveprojection,22Phantomlines,16Pictorialdrawings,1Plotsize,90Principaldimensionsandlayout,30–31Principalviews,27–28Printsize,90Projectiondefinitionof,21–22orthographic,23–24typesof,22–23

Projectionstandards,28–30,143–144

RRemovedsectionviews,74Requiredviewsandplacement,31–33Revisionblock,9–10,144Revolvedsectionviews,74–75

SScalefactor,142Screwfastenersfeatures,167standardthreads,167–168threadclass,168–169threadprofiles,167–168threadseries,168threadspecification,169–170

Sectiondrawingviewsaligned,75assembly,79auxiliary,77–78broken,76conceptsof,67–68constructing,81–83conventionalbreaklines,81cuttingplanelinestyles,69detail,77fullsectionviews,72generatingfromsolids,83–84half,76hatchpatterns,69–71offset,73partial,76removed,74representationandplacement,71–72revolved,74–75special,77straight,73typesof,72–80un-sectioned,79–80

Sectionlines,16Shaft-basisfitsystem,173–174Sheetlayoutbillofmaterials,9overviewof,7revisionblock,9–10titleblock,8–9zoning,8

Sheetorientation,6–7Smoothness,5Solidmodelsgeneratingauxiliaryviews,57–61generatingorthographicviews,37–39

Specialsectionviews,77Specificationdocuments,153–154

Spotface,99Standardmultiviewdrawing,33–37,39Standardparts,146Standardthreads,167–168Standardviews,30Stitchlines,17Straightsectionviews,73Surfacequality,142–143Surfaceroughness,183–184Surfacetexture,181Surfacetexturespecificationbasicspecification,183fullspecification,182generalspecification,183overviewof,181–182

Symbolicspecification,172

TTechnicaldrawings2D,1requirementsfor,2

Threadclass,168–169Threadprofiles,167–168Threadseries,168Threadspecification,169–170Titleblock,8–9,141Tracingpapers,6Trimetricprojections,133–1342Dtechnicaldrawings,1

UUnitsofangle,4–5Unitsoflength,4Un-sectionedsectionviews,79–80

VValuespecification,172–173Vellum,5Visible(object)lines,15

WWorkingdrawingsassembly,146–150checking,150–153componentdetaildrawings,144–146definitionof,139dimensionsandtolerances,142

drawingviews,140–141elementsof,140–144projectionstandard,143–144revisionblock,144scalefactor,142setof,154–158specificationdocuments,153–154standardparts,146surfacequality,142–143titleblock,141zoning,143

ZZone,8Zoning,8,143

••••••

OTHERTITLESINOURGENERALENGINEERINGANDK-12ENGINEERINGEDUCATIONCOLLECTIONJohnK.Estell,OhioNorthernUniversityandKennethJ.Reid,VirginiaTech,Editor

LeanEngineeringEducation:DrivingContentandCompetencyMasterybyShannonFlumerfelt,Franz-JosefKahlen,AnabelaAlves,

andAnnaBellaSiriban-Manalang

SustainableEngineeringbyKaufuiVincentWong

IntroductoryEngineeringMathematicsbyDavidReepingandKennethReid

CrackingtheCode:HowtoGetWomenandMinoritiesintoSTEMDisciplinesandWhyWeMust

byLisaM.MacLean

EngineeringDesignandtheProductLifeCycle:RelatingCustomerNeeds,SocietalValues,BusinessAcumen,andTechnicalFundamentals

byKennethJ.ReidandJohnK.Estell

MomentumPressisoneoftheleadingbookpublishersinthefieldofengineering,mathematics,health,andappliedsciences.MomentumPressoffersover30collections,includingAerospace,Biomedical,Civil,Environmental,Nanomaterials,Geotechnical,

andmanyothers.

MomentumPressisactivelyseekingcollectioneditorsaswellasauthors.FormoreinformationaboutbecominganMPauthororcollectioneditor,pleasevisit

http://www.momentumpress.net/contact

AnnouncingDigitalContentCraftedbyLibrariansMomentum Press offers digital content as authoritative treatments of advanced engineering topics byleaders in their field. Hosted on ebrary,MP provides practitioners, researchers, faculty, and students inengineering,science,and industrywith innovativeelectroniccontent insensorsandcontrolsengineering,advancedenergyengineering,manufacturing,andmaterialsscience.

MomentumPressofferslibrary-friendlyterms:

perpetualaccessforaone-timefeenosubscriptionsoraccessfeesrequiredunlimitedconcurrentusagepermitteddownloadablePDFsprovidedfreeMARCrecordsincludedfreetrials

http://www.momentumpress.net/contact

TheMomentumPressdigitallibraryisveryaffordable,withnoobligationtobuyinfutureyears.

Formoreinformation,pleasevisitwww.momentumpress.net/libraryortosetupatrialintheUS,[email protected].

http://www.momentumpress.net/library

mailto:[email protected]