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Engineering Graphics- Basics
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Overview of an Engineering Drawing
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GRAPHICS LANGUAGE
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1. Try to write a description of this object.
2. Test your written description by having someone attempt to make a sketch from your description.
Effectiveness of Graphics Language
The word languages are inadequate for describing the
size, shape and features completely as well as
concisely.
You can easily understand that …
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DRAWINGS( A Graphical Representation)
The Fact about:
If compared with Verbal or Written Description,Drawings offer far better idea about the Shape, Size & Appearance of any object or situation or location, that too in quite a less time.
Hence it has become the Best Media of Communication not only in Engineering but in almost all Fields.
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Graphic language in “engineering application” use
lines to represent the surfaces, edges and contours
of objects.
A drawing can be done using freehand, instruments or computer methods.
Composition of Graphic Language
The language is known as “drawing” or “drafting” .
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Freehand drawing The lines are sketched without using instruments other
than pencils and erasers.
Example
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Instrument drawing Instruments are used to draw straight lines, circles, and
curves concisely and accurately. Thus, the drawings are
usually 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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Engineering Drawing
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Elements of Engineering Drawing
Engineering drawing are made up of graphics language
and word language.
Graphicslanguage
Describe a shape(mainly).
Wordlanguage
Describe size, location andspecification of the object.
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Basic Knowledge for Drafting
Graphicslanguage
Wordlanguage
Linetypes
Geometricconstruction Lettering
Projectionmethod
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Drawing Standard
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Standards are set of rules that govern how technical
drawings are represented.
Drawing standards are used so that drawings convey
the same meaning to everyone who 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 für NormungDINGermany
Country Code Full name
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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 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
SCALE 1:X for reduction scales
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Basic Line Types
Types of Lines AppearanceName accordingto application
Continuous thick line Visible line
Continuous thin line Dimension line
Extension line
Leader line
Dash thick line Hidden line
Chain thin line Center line
NOTE : We will learn other types of line in later chapters.Engineering108.com
Visible lines represent features that can be seen in the
current view
Meaning of Lines
Hidden lines 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 lines indicate the sizes and
location of features on a drawing
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Example : Line conventions in engineering drawing
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Traditional Drawing Tools
Traditional Drawing 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
2H 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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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
Legibility - 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
Notes Title BlockEngineering108.com
Lettering StandardANSI Standard 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 least 1/3
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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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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5
Stroke Sequence
7
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6
8 9
0
Stroke Sequence
S 3
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Stroke Sequence
l i
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Stroke Sequencev w x k
z
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Stroke Sequencej y f
r
t
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Stroke Sequencec o a b
d p q e
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Stroke Sequenceg n m h
u s
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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
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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
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1. Place the little finger (or pencil’ s tip) at the center as a
pivot, and set the pencil point at the radius-distance from
the center.
2. Hold the hand in this position and rotate the paper.
Large Circle
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♣ The following figures illustrates the Aligned system of dimensioning:
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QUADRANT THEORY
FRP/V.P.
HRP/ H.P.
FRONTDIRECTION
X
Y
I
II
III
IV
FOUR QUADRANTS
TOPDIRECTION
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X
Y
1ST Quad.2nd Quad.
3rd Quad. 4th Quad.
X Y
VP
HP
Observer
THIS QUADRANT PATTERN, IF OBSERVED ALONG X-Y LINE ( IN RED ARROW DIRECTION)WILL EXACTLY APPEAR AS SHOWN ON RIGHT SIDE AND HENCE,IT IS FURTHER USED TO UNDERSTAND ILLUSTRATION PROPERLLY.
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♣ How to fold the A2 size drawing sheets for assignment work?♥ Mark 190 mm from the right edge of the drawing sheet. Mark 186 mm from the previous mark. Mark 20
mm from the left edge of the drawing sheet.♥ Mark 297 mm from the bottom edge of the drawing sheet on the reverse side. ♥ Coincide the first fold with third fold to get second fold. Coincide the third fold with the border line which
is 20 mm to the right of left edge of drawing sheet to get fourth fold. Fifth and sixth folds are back folds. ♥ All larger size drawing sheets i.e. A0, A1, A2 and A3 are folded to A4 size sheet.
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