c h a p t e r s i x 2d drawing representation. 2 technical drawing with engineering graphics, 14/e...

C H A P T E R S I X

2D DRAWING2D DRAWINGREPRESENTATIONREPRESENTATION

2Technical Drawing with Engineering Graphics, 14/eGiesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman

© 2012, 2009, 2003, Pearson Higher Education,Upper Saddle River, NJ 07458. • All Rights Reserved.

OBJECTIVESOBJECTIVES

1. Represent curved surfaces in multiview drawings

2. Show intersections and tangencies of curved and planar surfaces

3. Represent common types of holes

4. Show fillets, rounds, and runouts in a 2D drawing

5. Use partial views

6. Apply revolution conventions when necessary for clarity

7. Draw removed views and projected views

8. Show right- and left-hand parts

9. Project curved surfaces by points

10. Show and label an enlarged detail

11. Show conventional breaks



Common Manufactured Common Manufactured FeaturesFeatures

• Fillet

• Round

• Counterbore

• Countersink

• Spotface

• Boss

• Lug

• Flange

• Chamfer

• Neck

• Keyway/Keyseat

• Knurl

• Bushing



Conventional RepresentationsConventional Representations

Standard orthographic projections don’t always show complex shapes as clearly and simply as you may wish, so certain alternative practices, referred to as conventions, are accepted.

Conventions are like rules for breaking the rules. Note how these views are projected

Orthographic Views of Intersecting and Tangent Surfaces. (Lockhart, Shawna D.; Johnson, Cindy M., Engineering Design Communication: Conveying DesignThrough Graphics, 1st, © 2000. Printed and Electronically reproduced by permission of Pearson Education, Inc., Upper Saddle River, New Jersey.)



VISUALIZING AND DRAWING VISUALIZING AND DRAWING COMPLEX CYLINDRICAL SHAPESCOMPLEX CYLINDRICAL SHAPES

Steps



CYLINDERS WHEN SLICEDCYLINDERS WHEN SLICEDCylinders are often machined to form plane or other types of surfaces.

Normal surfaces appear true shape in the view where the line of sight is perpendicular to the surface. In the two other views that normal surface appears on edge. The back half remains unchanged.



CYLINDERS AND ELLIPSESCYLINDERS AND ELLIPSESIf a cylinder is cut by an inclined plane, the inclined surface is bounded by an ellipse. This ellipse will appear as a circle in the top view, as a straight line in the front view, and as an ellipse in the side view.

When a circular shape is shown inclined in another view and projected into the adjacent view it will appear as an ellipse, even though the shape is a circle.



INTERSECTIONS AND TANGENCIESINTERSECTIONS AND TANGENCIESWhere a curved surface is tangent to a plane surface no line is drawn, but when it intersects a plane surface, a definite edge is formed.

When plane surfaces join a contoured surface, a line is shown if they are tangent, but not shown if they intersect.



Intersections of CylindersIntersections of Cylinders

When the intersection is small, its curved shape is not plotted accurately because it adds little to the sketch or drawing for the time it takes. Instead it is shown as astraight line.

When the intersection is larger, it can be approximated by drawing an arc with the radius the same as that of the large cylinder.



FILLETS AND ROUNDSFILLETS AND ROUNDSA rounded interior corner is called a fillet. A rounded exterior corner is called a round.

(Courtesy of Ross Traeholt.)(Courtesy of Douglas Wintin.)

Rounds on a CAD Model of a Design for a Three-Hole PunchFillets on a CAD Model.



RUNOUTSRUNOUTSSmall curves called runouts are used to represent fillets that connect with plane surfaces tangent to cylinders.

Runouts from different filleted intersections will appear different owing to the shapes of the horizontal intersectingmembers.



CONVENTIONAL EDGESCONVENTIONAL EDGESThere is a conventional way of showing rounded and filleted edges for the sake of clarity. Added lines depicting rounded and filleted edges.

Rounded and filleted intersections eliminate sharp edges and can make it difficult to present the shape clearly.



NECESSARY VIEWSNECESSARY VIEWS

One-View Drawing

Two-View Drawing

Three-View Drawing

What are the absolute minimum viewsrequired to completely define an object?



PARTIAL VIEWSPARTIAL VIEWSA view may not need to be complete but needs to show what is necessary to clearly describe the object. This is called a partial view and is used to save sketchingtime and make the drawing less confusing to read.

You can use a break line to limit the partial view…

OR



Showing Enlarged DetailsShowing Enlarged Details

When adding a detail, draw a circlearound the features that will be included in the detail

Place the detail view on the sheet as you would a removed view. Label successive details with the word DETAIL followed by a letter, as in DETAILA, DETAIL B,



Conventional BreaksConventional BreaksTo shorten the view of a long object, you can use break lines…

Using a break to leave out a portion of the part, but allows the scale for the endsto be increased to show the details clearly.



ALIGNMENT OF VIEWSALIGNMENT OF VIEWSAlways draw views in the “standard” arrangement...

Because CAD makes it easy to move whole views, it istempting to place views where they fit on the screen orplotted sheet and not in the standard arrangement. This is not acceptable.

3D CAD software that generates 2D drawing views asprojections of the 3D object usually has a setting to select from third-angle or first-angle projection. Check your software if you are unsure which projection methods are available.

Because CAD makes it easy to move whole views, it istempting to place views where they fit on the screen orplotted sheet and not in the standard arrangement. This is not acceptable.

3D CAD software that generates 2D drawing views asprojections of the 3D object usually has a setting to select from third-angle or first-angle projection. Check your software if you are unsure which projection methods are available.



REMOVED VIEWSREMOVED VIEWSA removed view is a complete or partial view removed to another place on the sheet so that it is no longer in direct projection with any other view.

Removed View Using Viewing-Plane Line

Removed View Using View Indicator Arrow



RIGHT-HAND AND LEFT-HAND PARTSRIGHT-HAND AND LEFT-HAND PARTSOften, parts function in pairs of similar opposite parts, but oppositeparts can rarely be exactly alike.

On sketches and drawings a left-hand part is noted as LH, and a right-hand part as RH.



REVOLUTION CONVENTIONSREVOLUTION CONVENTIONSRegular multiview projections are sometimes awkward, confusing, or actually misleading.

Revolutions like these are frequently used in connection with sectioning. Revolved sectional views are called aligned sections.



Common Hole Features Shown in Common Hole Features Shown in Orthographic ViewsOrthographic Views



Common Features Shown in Orthographic Common Features Shown in Orthographic ViewsViews



Common Features Shown in Orthographic Common Features Shown in Orthographic Views Continued…Views Continued…

c h a p t e r s i x 2d drawing representation. 2 technical drawing with engineering graphics, 14/e...

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