7. INTRODUCTION TO ENGINEERING GRAPHICS
Drawings prepared by Engineers of engineering
objects are known as Engineering Drawings
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Engineering Graphics is a Graphics Language
used by Engineers to convey ideas of an object
clearly and accurately.
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BIS (Bureau of Indian Standards) has published
various standards for different subjects.
8. DRAWING INSTRUMENTS
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Drawing Board
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T square or Mini Drafter
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Set Square
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Protractor(180deg-360deg)
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Engineers Scale Set
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Instrument Box
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Stencil
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French Curve
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Ruling Pens
22. ELEMENTS OF DIMENSIONING
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1) Projection Line
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2) Dimension Line
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3)Leader Line
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4)Dimension Line Termination
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5)Origin Indication
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6)Dimension
23. ●
Projection Line:
A continous thin line should be extended beyond respective
dimension line.
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Should not cross other lines if possible
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Intersecting projection and dimension should be avoided.
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24. ●
DIMENSION LINE(Continous Thin Line)
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Dimesion lIne should not cross other lines.
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Centre lines or Outlines should not be used as Dimension Line.
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Dimension Line should be drawn from visible outline.
26. ●
Dimension Line Termination
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It carries arrow head or oblique strokes at their end.
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The arrowhead may be open,closed or closed filled in.
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In a drawing only one style of arrowhead termination should be used.
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29. Arrangement of Dimensioning
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Different arrangement indicate dimension based on design
requirements
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The main arrangements of Dimensioning are:
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Chain Dimensioning
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Parallel Dimensioning
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Superimposed Dimensioning
32. ●
Superimposed Running Dimensioning
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It is a simplified parallel Dimensioning.
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May be used where there is a space limitations.
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Origin should be indicated properly.
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One end should be terminated at origin while other end should carry
arrowhead
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33.
34. 3.Geometerical Constructions
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Terminology
a) Point: A dimensionless location where 2 lines intersect.
b) Line: Having specific length,having no breadth and thickness.
c)Circle: Path described by a point moving in a plane at a fixed distance(Radius)
and fixed point(Centre).
d) Angle: Formed by 2 intersecting lines. Measured in degrees.
e)Acute Angle: Angle having less than 90 deg
f)Obtuse Angle: Angle having greater than 90 deg.
g)Triangle:Bounded by 3 straight lines.
h) Rectangle: Having 4 sides and 2 sides equal.
i) Square: 4 Sided figure having 2 diagonals intersecting at right angles.
35. j)Rhombus: Four sided figure having 2 diagonals of unequal length intersecting.
k) Trapeizum:Four sided fig having opposites sided parallel.
l)Polygon: Multisided figure.
m) Regular Polygon: Multisided fig having length of sided equal and angles equal.
n)Regular Pentagon: Having 5 equal sides and included angle 72 deg
o) Regular Hexagon: Having 6 equal sided and included angle 120 deg
p)Regular Heptagon:Having 7 equal sided and included angle 128.6deg
q) Regular Octagon: Having 8 equal sidd and included angle 135 deg
r)Diameter of a Circle: Terminated Line passing through the centre of circle,
s) Chord of a circle: A line other than its diameter
t)Sector: Part of circle containing 2 radii and arc between them.
41. 4.SCALES●
For drawing small objects like electronic component ,wrist watches need to
draw larger size than the objects. Such drawings prepared to an enlarges size
is called ENLARGED SCALE DRAWING
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Drawings made to same size as object which it represents ,the drawing
obtained is known as FULL SCALE DRAWING OR FULL SIZE DRAWING
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Drawing prepared proportionally to smaller or larger size than actual size are
said to be made up of SCALE
Scale of a drawing may be defined as ratio of Linear Dimension of an object in
a drawing to the actual linear dimension of same object .
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Representative Fraction: may be defined as ratio of linear Distance between
any two points of the object on a drawing to the actual distance between the
same points of the object represented as (R.F)
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R.F=DISTANCE ON DRAWING/DISTANCE ON OBJECT
42. Plain Scale:
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A plain scale is the simplest scale shows only 2 consecutive units
such as millimeter(mm) ,centimeter(cm)and decimetre(dm).
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Here a line is divided into many number of equal parts or units(say
cm) and each unit is divided into no of parts say millimeter
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For construction plain scale needed to be :Representative fraction
scale ,Measuring Units of scale ,Maximum units to be measured.
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46. ●
VERNIER SCALE
It is a modified form of Diagonal Scale.
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A short scale constructed along with plain scale to measure fraction
to the smallest division of the plain scale.
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A vernier scale has 2 parts:a)Fixed Scale: Main Scale
b)Movable Scale: Vernier Scale
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Vernier Scale slides on the side of main scale and both of them are
used together to measure small divisions upto 3 divisions,
54. Parabola
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A parabola is a curve that looks like the one
shown above. Its open end can point up, down,
left or right. A curve of this shape is called
'parabolic', meaning 'like a parabola'.
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The most common example is when you stir up
orange juice in a glass by rotating it round its axis.
... Parabolas are also used in satellite dishes to
help reflect signals that then go to a receiver.
