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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
Stroke Sequence : Upper-case
Skip section
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N M K Z
Y A 4
Stroke Sequence : Upper-case
Skip section
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O Q C G
Stroke Sequence : Upper-case
Skip section
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D U P B
R J
Stroke Sequence : Upper-case
Skip section
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5 7Stroke Sequence : Upper-case
1 2
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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
Stroke Sequence : Lower-case
Skip section
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j y f
r
t
Stroke Sequence : Lower-case
Skip section
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c o a b
d p q e
Stroke Sequence : Lower-case
Skip section
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g n m h
u s
Stroke Sequence : Lower-case
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