ISOMETRIC PROJECTION
Part II
Prof.T.JEYAPOOVAN
Department of Mechanical Engineering
Hindustan Institute of Technology and Science
Chennai-603103, India
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Isometric Projection and
Isometric Scale
• Isometric projection is
always used for
combination of solids.
• To draw isometric
projection, isometric
dimensions are used which
is 0.82× True length.
• A conversion scale used for
converting true dimensions
into isometric dimensions is
shown in fig.
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Example1: Draw the isometric projection of a frustum of a cone of base
diameter 60 mm, top base diameter 35 mm and axis length 50 mm rests on
HP on its base.
• Draw TV and FV of the frustum of
cone using isometric scale.
• A square box of exact size is used
in TV to enclose the frustum and
construct the box in isometric.
• Use 4-centre method to draw
bottom base in isometric.
• Draw another square to enclose top
base of frustum in TV and locate it
in isometric as shown.
• Repeat the 4-centre method to
complete top base in isometric.
• Draw extreme generators and
darken visible portion of the solid to
complete isometric projection.
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Example 2: Draw the isometric projection of a hexagonal prism of side of
base 40 mm and height 60 mm with a right circular cone of base 40 mm as
diameter and altitude 50 mm, resting on its top such that the axes of both
solids are collinear.
• Draw the TV and FV of the prism
using isometric scale.
• A rectangular box of exact size is
used to enclose the prism.
• Construct the box in isometric.
• Measure the corners from TV and
mark them on the sides of the box.
• Repeat the procedure for cone but
construct it above the prism.
• Darken the top, left and right
edges of the prism and the visible
portion of the objects to complete
the isometric projection.
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Example 3: A square pyramid having a side of 50 mm base and 75 mm as
axis height stands centrally on circular block of 100 mm diameter and 50
mm thick. The base edges of the pyramid are parallel to VP. Draw the
isometric projection of the two objects.
• Draw the TV and FV of the
cylinder using isometric scale.
• A square box of exact size is
used to enclose the cylinder.
• Construct the box in isometric.
• Use 4-centre method to draw top
base in isometric and repeat the
same procedure for bottom base.
• Repeat the procedure for square
pyramid but construct it above
the cylinder.
• Darken the visible portion of the
cylinder and square pyramid to
complete isometric projection.
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Example 4: A sphere of diameter 40 mm rests centrally on top of a cube of
side 50 mm. Draw the isometric projection of the solids.
• Draw the TV and FV of the cube
using isometric scale.
• Construct the cube in isometric
which is of same size as the box.
• Note that isometric projection of a
sphere is a circle of true diameter.
• Mark the centre of the circle
above the top face of cube at a
height of 0.82 × radius. Then
draw the circle with this centre
with TRUE radius.
• Darken the circle and visible
portion of the cube to complete
isometric projection.
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Tips to draw Isometric Projection
• To draw isometric projection, the top and front views are
always drawn in isometric dimensions which will be used
to construct the isometric projection.
• Always isometric dimensions are used to draw the
isometric drawing of combination of solids involving
sphere or spherical shape.
• Isometric projection of a sphere is always a circle of TRUE
radius/diameter.
• In isometric projection, importance is given to the 3D
picture of the objects, so marking, dimensioning and
hidden lines may be omitted.
• Complete the isometric drawing by clearly drawing dark
lines for the visible portion of the objects.
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REFERENCE BOOKS
1. Jeyapoovan T, “Lesson Plans for Engineering
Graphics”, 2010, Vikas Publishing House Pvt
Ltd, New Delhi.
2. Jeyapoovan T, “Engineering Drawing and
Graphics”, 2011, Vikas Publishing House Pvt
Ltd, New Delhi.
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End of Lesson 12
Thank You
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