drawing lec 01 introduction 1

Engineering Drawing

By: Engr. Rauf Ahmad

Chapter 1Introduction

LEC 01, Introduction 2

Contents

Drawing standards

Engineering drawing

Drawing sheetScaleLetteringLine types


The things you need


Items required for drawing Items required for drawing

Drawing board (Available in Drawing Halls)Drawing sheet (Half Scholar Sheet)Mini-drafter/drafting machine/T- square(2ft or 3ft)Instrument box containing compass, divider, etc.Scales(6in. or 12in.)Set-Squares & Protractor(30cm)French curves(not required)Drawing pencils(A lots of them)Eraser(smooth)Drawing clip/pin/adhesive tapeSharpenerDuster


Standard sizes of drawing sheets as per BIS

A2 sizeLEC 01, Introduction 6

Instrument DrawingDrawing Pencils

High-quality drawing pencils should be used in technical drawing, never ordinary writing pencils.

Many makes of mechanical pencils are available together with refill leads in all grades. Choose a mechanical pencil that feels comfortable in your hand.


Drawing Pencils

Wooden pencils – are graded and designated by numbers and lettersMechanical clutch pencils – Not allowed• 7B, 6B, 5B, 4B, 3B, 2B, B - in decreasing order of softness and blackness• HB to F – Medium grade• H, 2H, 3H, 4H, 5H, 6H, 7H, 8H, 9H – increasing order ofhardness.

Drawings are done using 2H pencils and finished with Hand HB pencils – to be practiced in this course.


Grades and designation of wooden pencilsLEC 01, Introduction 9

Pencil drawing –In finished drawing, all lines (except construction lines- used to construct the drawing) should be dense, clean and uniform. Construction line should be drawn very thin and should be hardly visible in the finished drawing ( they should not be erased).


Line types


Line types….CONTD


EngineeringDrawing

The words of the language, as they are written or spoken, do not seem to play any role in my mechanism of thought. The psychical entities which seem to serve as elements in thought are certain signs and more or less clear images which can be “voluntarily” reproduced and combined--this combinatory play seems to be the essential feature in productive thought before there is any connection with logical construction in words or other kinds of signs which are communicated to others

--Albert Einstein

Contents

1. Try to write a description of this object.

2. Test your written description by having someone attempt to make a sketch or visualize from your description.

Effectiveness of Graphic Language

The word language is inadequate for describing the sizesize,

shapeshape and featuresfeatures completely as well as concisely.

You can easily understand that …


Graphic Language inEngineering Drawing

“Engineering drawing” or “blueprint” uses llinesines torepresent the features features of an object.

Features of an object are surface surface (include planeplane) and

edgeedge.

Surface

Edge


A drawing can be created in 3 ways

Ways to Create anEngineering Drawing

1. Freehand sketch

2. Using typical drawing instruments

3. Using a computer


Example

Create a Drawing : Freehand sketch

The lines are drawn using only pencil and erasers on a blank or grid paper.

Pictorial sketch Orthographic sketchLEC 01, Introduction 17

Example

Create a Drawing : Using instruments

Drawing instruments are used to draw straight lines, circles, and curves conciselyconcisely and accuratelyaccurately.

Drawings are usually made to scalemade to scale.


Example

Create a Drawing : Using a computer

Computer aided drafting (CAD) software is used.

2D drawing Solid modelingLEC 01, Introduction 19

Elements of a DrawingA clear and precise engineering drawing requires both

graphics graphics and word word languages.

Graphics language

Describe a shape (mainly).

Word language

Describe an exact size, location and specificationof the object.


Text on drawings : Example

Generalnotes Title

block

Dimensions&

Notes


Knowledge and Skills Require

Graphicslanguage

Wordlanguage

Dimensions & Notes

VisualizationVisualization is the ability to mentally picture things that do not exists.

VisualizationUsing line types

Geometricconstruction

Projectionmethod

Engineering Drawing

ContentsLEC 01, Introduction 22

Drawing Standard

Drawing sheet Scale Lettering Line types Contents

Definition and Necessity

Drawing standards are set of rulesset of rules that govern how

technical drawings are represented.

Drawing standards are used so that drawings conveyconveythe same meaningthe same meaning to everyone who reads them.


ISO International Standards Organization

Standard Code

ANSI American National Standard InstituteUSA

JIS Japanese Industrial StandardJapan

BS British StandardUK

AS Australian StandardAustralia

Deutsches Institut für NormungDINGermany

Country Code Full name

มอก./TISสำ�นักง�นม�ตรฐ�นผลิตภัณฑ์อุตส�หกรรมThailand


Examples of TIS Standard

มอก. 210 2520 วธิเีขยีนแบบท่ัวไป : ท�งเครื่องกลมอก 440. ล 12541. ก�รเขยีนแบบก่อสร�้งเล่ม 1 ท่ัวไป

มอก 446 ล 42532ขอ้แนะนำ�สำ�หรบัก�รเขยีนแผนภ�พวงจรไฟฟ�้มอก 1473 2540 ก�รเขยีนแบบเทคนิค ก�รติดต้ัง

สญัลักษณ์สำ�หรบัระบบท่อของเหลวระบบทำ�คว�มรอ้น ก�รระบ�ยอ�ก�ศและระบบท่ออ�ก�ศ

Code number Contents

ท่ีม� : http://library.tisi.go.th/data/lib_resources/pdf/catalog-online49/tis/02_ICS.pdfLEC 01, Introduction 26

JIS Z 8311 Sizes and Format of DrawingsSizes and Format of Drawings

JIS Z 8312 Line ConventionsLine ConventionsJIS Z 8313 LetteringLettering

JIS Z 8314 ScalesScales

JIS Z 8315 Projection methods

JIS Z 8316 Presentation of Views and Sections

JIS Z 8317 Dimensioning

Code number Contents

Examples of JIS Standard


Drawing StandardDrawing Sheet

Drawing standard Contents

Drawing Sheet : Standard size

Trimmed paper ofa size A0 ~ A4.

Standard sheet size (JIS)

A4 210 x 297A3 297 x 420A2 420 x 594A1 594 x 841A0 841 x 1189

A4

A3

A2

A1

A0(Dimensions in millimeters)


Drawing space

Drawingspace

Title block

d

d

c

c

cBorder lines

1. Type X (A0~A4)

2. Type Y (A4 only)

Title block

Sheet size c (min) d (min)

A4 10 25 A3 10 25 A2 10 25 A1 20 25 A0 20 25

Drawing Sheet : Orientation & Margin


Drawing StandardDrawing Scale


Drawing Scales : Definition

Drawing Actual

Length, size

:

ScaleScale is a ratio between the linear dimension of a drawn representation of an object and the actual object.

1 2


Designation of a scale consists of the word “SCALE” followed by the indication of its ratio, as follows

SCALE 1:1 for full sizeSCALE X:1 (X > 1) for an enlargementenlargement scalesSCALE 1:X (X > 1) for a reductionreduction scales

Drawing Scales : Designation

Drawing scale is commonly found in a title block.


Dimension numbersDimension numbers shown in the drawing representthe “true size” of an object and they are independent ofthe drawing scale used.

Drawing Scales : Notes


Standard reducing scales are1:2, 1:5, 1:10, 1:20, 1:50, 1:100

Drawing Scales : Standard scale

Standard enlarging scales are2:1, 5:1, 10:1, 20:1, 50:1, 100:1


Drawing StandardLettering


- Size (or text height)- line thickness

- Shape- Space between letters- Space between words

Recommendation

LegibilityLegibility

UniformityUniformity

Text’s style on the drawingmust have the following2 properties

Examples

GOOD

Not uniform in style.

Not uniform in height.

Not uniformly vertical.

Not uniform inthickness of stroke.

Inappropriate spacebetween letters


Style (this course)

Gothic vertical style.

Begin the sentence, phrase or word with a capital letter.

Text height 2~3 mm.

Space between lines of text is about of text height.

Height of the lower-case letter is about 2/3 of that of a

capital letter.


Basic StrokesStraight Slanted CurvedHorizontal

1 1 2

3

“I” letter “A” letter

1

2

3

4 5

6

“B” letter

Examples


Suggested Strokes SequenceStraight line

letters

Curved lineletters

&Numerals

Upper-case Letters & Numerals


Lower-case Letters


I L T F

E H

Stroke Sequence : Upper-case

Skip sectionLEC 01, Introduction 42

V X W



N M K Z

Y A 4



O Q C G



D U P B

R J



5 7


1 2


6

8 9

0S 3



l i

Stroke Sequence : Lower-case


v w x k

z



j y f

r

t



c o a b

d p q e



g n m h

u s



DRAWING

Word Composition

Non-uniformspacing

Uniformspacing DR A WING

Space between the letters depends on the adjacentcontour of the letters.

Word having non-uniform spacing is more readable.LEC 01, Introduction 54

Word Composition

Contour

DRAWINGContour can be denoted as “straight”, “slant” and “curve”.

Adjacent contour can be1. straight-straight : II, IN, IM, IP etc.2. straight-curve (or curve-straight) : IO, QR etc.

3. straight-slant (or slant-straight) : IV, IW etc.

4. curve-curve : OO, OG etc.

5. slant-curve (or curve-slant) : VO, WG, VC etc.

6. slant-slant : VW, VX etc.

Spa

cing


Leave the space between words equal to the spacerequires for writing a letter “O”.

Example

Sentence Composition

ALL DIMENSIONS ARE INMILLIMETERS

O O OO UNLESS

OTHERWISE SPECIFIED.O


Drawing StandardLine Types


Basic Line Types &Name according to application

ContinuousDashChain

Style

Thickness Thick Thin 1. Dimension line2. Extension line3. Leader line

Center line

Hidden line

Visible line

represent features that can be seen in the current view.

represent features that can not be seen in the current view.

represents symmetry, path of motion, centers of circles,

axis of axisymmetrical parts

indicate the sizes and location of features.

1. Visible line

3. Hidden line

4. Center line

2. Dimension line Extension line Leader line


Example

ContentsLEC 01, Introduction 59