Basic Principle of Technical Drawing

7/29/2019 Basic Principle of Technical Drawing

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BASIC PRINCIPLEOF TECHNICAL DRAWING

Boni Sena, S.T., M.Eng.


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ENGINEERING

An engineer needs universal

language to communicate with

all parts of engineering system


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DRAWINGIS UNIVERSALLANGUAGE

House

What do you think about the word of house and the picture of house ?

The picture of house has deeper understanding than the word of house

Picture is not

enough tocommunicate


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MANUFACTURINGSYSTEMProduct

Design DrafterOperator

We cant order the operator to

make a product only use

picture without standard


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CANYOUTELLTHEDIFFERENCEBETWEENTWOPICTURESBELOW ?

The line is not straightThe line is straight

No sizesize

Which one is the best picture in your opinion ? Explain your answer !


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CREATE A DRAWING : MANUAL

Using free hand to drawan object

Using drawing tools to draw

object


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CREATE A DRAWING : COMPUTER AIDEDDESIGN (CAD)

Computer aided drafting (CAD) software is used.

Example of CAD is AutoCAD


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DRAWING TOOLS (MANUAL)


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COMPUTER AIDED DESIGN (CAD)


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SEETHEEXAMPLEOFTECHNICALDRAWINGBELOW

Dimension

Object

LinesTitle Block


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ELEMENTSOF ENGINEERING DRAWING

Graphics

language

Word

language

Dimensions & Notes

VisualizationUsing line types

Geometric

construction

Projection

method

Engineering Drawing

Standard for Engineering Drawing


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ISO International Standards Organization

Standard for Engineering Drawing

ANSI American National Standard InstituteUSA

JIS Japanese Industrial StandardJapan

BS British StandardUK

AS Australian StandardAustraliaDeutsches Institut frNormungDINGermany

Country Code Full name

./TIS Thailand


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DRAWING SHEET : STANDARDSIZE

Trimmed paper ofa size A0 ~ A4.

Standard sheet size

(JIS)

A4 210 x 297

A3 297 x 420

A2 420 x 594A1 594 x 841

A0 841 x 1189

A4

A3

A2

A1

A0(Dimensions in millimeters)


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Drawing space

Drawing

space

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 25A0 20 25

Drawing Sheet : Orientation & Margin


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START DRAWING !


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Drawing Scales : Definition

Drawing Actual

Length, size

:

Scale is a ratio between the linear dimension of adrawn representation of an object and the actual object.

1 2


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Designation of a scale consists of the word SCALE

followed by the indication of its ratio, as follows

SCALE 1:1 for full size

SCALE X:1 (X > 1) for an enlargement scales

SCALE 1:X (X > 1) for a reduction scales

Drawing Scales : Designation

Drawing scale is commonly found in a title block.


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- Size (or text height)

- line thickness

- Shape

- Space between letters

- Space between words

Recommendation

Legibility

Uniformity

Texts style on the drawing

must have the following

2 propertiesExamples

GOOD

Not uniform in style.

Not uniform in height.

Not uniformly vertical.

Not uniform in

thickness of stroke.

Inappropriate space

between letters


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BASIC STROKESStraight Slanted CurvedHorizontal

1 1 2

3

I letter A letter

1

2

3

4 5

6

B letter

Examples


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Suggested Strokes Sequence

Straight line

letters

Curved line

letters

&

Numerals

Upper-case Letters & Numerals


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Lower-case Letters


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I L T F

E H

Stroke Sequence : Upper-case

Skip section


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V X W


Skip section


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N M K Z

Y A 4


Skip section


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O Q C G


Skip section


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D U P B

R J


Skip section


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5 7Stroke Sequence : Upper-case

1 2

Skip section


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6

8 9

0S 3Stroke Sequence : Upper-case

Skip section


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l i

Stroke Sequence : Lower-case

Skip section


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v w x k

z


Skip section


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j y f

r

t


Skip section


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c o a b

d p q e


Skip section


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g n m h

u s


Skip section


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DRAWING

Word Composition

Non-uniform

spacing

Uniform

spacing

DRA W IN G

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

Word having non-uniform spacing is more readable.


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Word Composition

ContourDRAWING

Contour can be denoted as straight, slant and curve.

Adjacent contour can be

1. 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.

Spacing


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

Example

Sentence Composition

ALL DIMENSIONS ARE IN

MILLIMETERS

O O O

OUNLESS

OTHERWISE SPECIFIED.O


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DRAWING STANDARDLINE TYPES

Drawing standard Contents

B i Li T &


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Basic Line Types &

Name according to application

ContinuousDashChain

StyleThickness Thick Thin 1. Dimension line

2. Extension line3. Leader line

Center lineHidden 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 lineLeader line


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Example

Documents

Basic Principle of Technical Drawing