chapter 01 introduction
DESCRIPTION
engineering graphics-ITRANSCRIPT
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Chapter 1Overview of an
Engineering Drawing
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TOPICS
Drawing standards
Graphics language
Engineering drawing
Traditional Drawing Tools
Lettering
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GRAPHICSLANGUAGE
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1. Try to write a description ofthis object.
2. Test your written description
by having someone attemptto make a sketch from your
description.
Effectiveness of Graphics Language
The word languages are inadequate for describing the
size, shape and featurescompletely as well as
concisely.
You can easily understand that
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Graphic languagein engineering application use
l inesto represent the surfaces, edges and contours
of objects.
A drawing can be done using freehand, ins t ruments
or computer methods.
Composition of Graphic Language
The language is known as drawing or draft ing .
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Freehand drawingThe lines are sketched without using instruments other
than pencils and erasers.
Example
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Instrument drawingInstruments are used to draw straight lines, circles, and
curves concisely and accurately. Thus, the drawings areusually made to scale.
Example
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Computer drawing
The drawings are usually made by commercial software
such as AutoCAD, solid works etc.
Example
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EngineeringDrawing
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Elements of Engineering Drawing
Engineering drawing are made up of graphics language
and wo rd language.
Graphicslanguage
Describe a shape
(mainly).
Word
language
Describe size, location and
specification of the object.
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Basic Knowledge for Drafting
Graphics
language
Word
language
Line
types
Geometric
construction LetteringProjection
method
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Drawing Standard
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Introduction
Standardsare set of rules that govern how technicaldrawings are represented.
Drawing standards are used so that drawings convey
the same meaning to everyonewho reads them.
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ISO International Standards Organization
Standard Code
ANSI American National Standard InstituteUSA
JIS Japanese Industrial StandardJapan
BS British StandardUK
AS Australian StandardAustralia
Deutsches Institut frNormungDINGermany
Country Code Full name
. Thailand
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Partial List of Drawing Standards
.210 2520 : . 440 .1 2541 1 . 446.4 2532
. 1473 2540
Code number Contents
: http://library.tisi.go.th/data/lib_resources/pdf/catalog-online49/tis/02_ICS.pdf
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Partial List of Drawing Standards
JIS Z 8311 Sizes and Form at of Drawing s
JIS Z 8312 Line Convent ions
JIS Z 8313 Letter ing
JIS Z 8314 Scales
JIS Z 8315 Projection methods
JIS Z 8316 Presentation of Views and Sections
JIS Z 8317 Dimensioning
Code number Contents
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Drawing Sheet
Trimmed paper ofa size A0 ~ A4.
Standard sheet size
(JIS)
A4 210 x 297
A3 297 x 420
A2 420 x 594
A1 594 x 841
A0 841 x 1189
A4
A3
A2
A1
A0(Dimensions in millimeters)
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Drawing space Drawing
spaceTitle block
d
d
c
c
cBorder
lines
1. Type X(A0~A4) 2. Type Y(A4 only)
Orientation of drawing sheet
Title block
Sheet size c (min) d (min)
A4 10 25A3 10 25
A2 10 25
A1 20 25
A0 20 25
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Drawing Scales
Scaleis the ratio of the linear dimension of an element
of an object shown in the drawing to the real linear
dimension of the same element of the object.
Size in drawing Actual size
Length, size
:
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Drawing Scales
Designation of a scale consists of the word SCALE
followed by the indication of its ratio, as follow
SCALE 1:1 for full size
SCALE X:1 for enlargement scales (X > 1)SCALE 1:X for reduct ion scales (X > 1)
Dimension numbers shown in the drawing are correspond
to true size of the object and they are independentof
the scale used in creating that drawing.
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Basic Line Types
Types of Lines Appearance
Name according
to application
Continuous thick line Visible line
Continuous thin line Dimension lineExtension line
Leader line
Dash thick line Hidden line
Chain thin line Center line
NOTE : We will learn other types of line in later chapters.
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Visib le l ines represent features that can be seen in thecurrent view
Meaning of Lines
Hidden l ines represent features that can not be seen in
the current view
Center line represents symmetry, path of motion, centers
of circles, axis of axisymmetrical parts
Dimension and Extension l ines indicate the sizes and
location of features on a drawing
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Example: Line conventions in engineering drawing
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TraditionalDrawing Tools
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DRAWING TOOLS
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1. T-Square 2. Triangles
DRAWING TOOLS
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3. Adhesive Tape 4. Pencils
H or HB for thick line4H for thin line
DRAWING TOOLS
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5. Sandpaper 6. Compass
DRAWING TOOLS
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7. Pencil Eraser 8. Erasing Shield
DRAWING TOOLS
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9. Circle Template 10. Tissue paper
DRAWING TOOLS
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11. Sharpener 12. Clean paper
DRAWING TOOLS
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ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLM
NOPQRSTUVWXYZABCDEF
ABCDEFGHIJKLMNOPQRST
UVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEF
Lettering
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Text on Drawings
Text on engineering drawing is used :
To communicate nongraphic information.
As a substitute for graphic information, in those instance
where text can communicate the needed information
more clearly and quickly.
Uniformity - size
- line thickness
Legibi l i ty - shape
- space between letters and words
Thus, it must be written with
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Example Placement of the text on drawing
Dimension & Notes
NotesTitle Block
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Lettering Standard
ANSIStandard This course
Use a Gothic text style,
either inclined or vertical.
Use all capital letters.
Use 3 mm for most
text height.
Space between lines
of text is at least1/3
of text height.
Use only a vertical Gothic
text style.
Use both capital and
lower-case letters.
Same. For letters in title
block it is recommend to use
5~8 mm text height
N/A.
Follows ANSI rule.
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Basic Strokes
Straight Slanted CurvedHorizontal
1 1 2
3
Examples :Application of basic stroke
I letter A letter 1
2
3
4 5
6
B letter
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Suggested Strokes Sequence
Straight lineletters
Curved line
letters
Curved lineletters &
Numerals
Upper-case letters & Numerals
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The text s body height is about 2/3the height of a capital
letter.
Suggested Strokes SequenceLower-case letters
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Stroke Sequence
I L T F
E H
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V X W
Stroke Sequence
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N M K Z
Y A
Stroke Sequence
4
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O Q C G
Stroke Sequence
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D U P B
R J
Stroke Sequence
1 2
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5Stroke Sequence
7
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6
8 9
0Stroke Sequence
S 3
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Stroke Sequence
l i
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Stroke Sequence
v w x k
z
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Stroke Sequence
j y f
r
t
S k S
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Stroke Sequence
c o a b
d p q e
St k S
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Stroke Sequence
g n m h
u s
W d C iti
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Word Composition
Look at the same word having different spacing between letters.
JIRAPONG
JI GOR NPAWhich one is easier to read ?
A) Non-uniform spacing
B) Uniform spacing
W d C iti
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Word Composition
JIRAPONG\/ \| )( )| (|
Space between the letters depends on the contour of
the letters at an adjacent side.
Spacing
Contour ||||General conclusions are:
Good spacing creates approximately equal background
areabetween letters.
S b t L tt
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1. Straight - Straight
2. Straight - Curve
3. Straight - Slant
4. Curve - Curve
Space between Letters
S b t L tt
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6. Slant - Slant5. Curve - Slant
7. The letter L and T
slant slant
slant
straight
Space between Letters
Example : Good and Poor Lettering
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GOOD
Not uniform in style.
Not uniform in height.
Not uniformly vertical or inclined.
Not uniform in thickness of stroke.
Area between letters not uniform.
Area between words not uniform.
Example: Good and Poor Lettering
S t C iti
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Leave the space between words equal to the space
requires for writing a letter O.
Example
Sentence Composition
ALL DIMENSIONS ARE IN
MILLIMETERS
O O O
OUNLESS
OTHERWISE SPECIFIED.O
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End of Chapter 1Overview of an
Engineering Drawing