1. ISOMETRIC PROJECTION
Part I
Prof.T.JEYAPOOVAN
Department of Mechanical Engineering
Hindustan Institute of Technology and Science
Chennai-603103, India
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2. Isometric axes and Isometric Line
• Isometric view or
projection shows all three
dimensions of an object
which are useful to
understand and visualize an
object.
• There are 3 isometric axes
with an angle of 120º
between them.
• Any line drawn parallel to
an isometric axis is called
isometric line.
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3. Isometric View and Isometric Projection
• To draw isometric view true
dimensions are used.
• Isometric view is used for
single solid.
• To draw isometric projection,
isometric dimensions are used
which is 0.82× True length.
• Isometric projection is used for
combination of solids.
• Consider isometric projection
and isometric view of a
rectangular prism shown in fig.
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4. Box Method
• Box method is used to
draw isometric view or
projection of an object.
• A rectangular or square box
of suitable size is used to
enclose the object in such a
way that some of the
corners or edges touch the
box sides.
• Construct the isometric
view/projection of the box
using the isometric axes.
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5. Example 1: A hexagonal prism of base side 30 mm and axis length 60
mm is resting on HP on its base with a side of base parallel to VP. Draw
the isometric view of the prism.
• Draw the TV and project the FV of
the prism.
• A rectangular box of exact size is
used to enclose the prism in TV
such a way that some of the
corners or edges touch box sides.
• Draw two isometric axes at 30°
and construct the box in isometric.
• Measure the corners of the prism
from TV and mark them on the
sides of the box in isometric.
• Darken the top, left and right edges
of the prism to complete the
isometric view.
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6. Example 2: Draw the isometric view of a hexagonal prism of base side
30 mm and axis length 60 mm rests on HP on one of its rectangular
faces with its axis perpendicular to VP.
• Draw FV and TV of the prism.
• A rectangular box of exact size
is constructed horizontally to
enclose the prism in such a way
that some of the corners or edges
touch the box sides.
• Draw one isometric axis at 30°
and another vertical to construct
the box horizontally in isometric
• Measure the corners of the prism
from FV and mark them on the
sides of the box.
• Darken the right, left and top
edges of the prism to complete
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the isometric view.

7. 4-Centre Method
• 4-Centre method is used
to draw an ellipse in
isometric for a circle.
• Construct the rhombus in
isometric using circle
diameter as sides.
• Draw arcs using 4-centres
m,n,1 and 3 with radius
shown fig.
• For isometric projection,
isometric scale is used to
draw the rhombus.
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8. Example 3: Draw the isometric view of a vertical cylinder of base diameter
50 mm and axis length 60 mm.
• Draw TV and FV of the cylinder.
• A square box of exact size is used
to enclose the cylinder.
• Construct the box in isometric.
• Use 4-centre method to draw the
top base as an ellipse in isometric
and repeat the same procedure for
bottom base.
• Draw left and right extreme
generators.
• Darken the top, left and right
visible portion of the cylinder to
complete the isometric view.
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9. Example 4: Draw the isometric view of a vertical cylinder of base
diameter 50 mm and axis length 60 mm.
• Draw FV and TV of the cylinder.
• A square box of exact size is
used to enclose the cylinder.
• Construct the box horizontally in
isometric.
• Use 4-centre method to draw the
front base as an ellipse in
isometric and repeat the same
procedure for rear base.
• Draw top and bottom generators.
• Darken the top, left and right
visible portion of the cylinder to
complete the isometric view.
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10. Example 5: A pentagonal pyramid of base side 30 mm and axis length 65
mm is resting on HP on its base with a side of base perpendicular to VP. It
is cut by a plane inclined at 30° to HP and perpendicular to VP and passes
through a point at a distance 30 mm from the apex. Draw the isometric view
of the remaining portion of the pyramid.
• Draw TV, FV of pyramid and cutting
plane at 30° to XY.
• Draw a rectangle to enclose base of
pyramid in TV and rhombus in
isometric to mark base corners.
• Produce a new corner to touch the
side of rectangle like m, then mark it
on the sides of rhombus.
• Draw a line from m parallel to an
isometric axes.
• Measure the horizontal distance from
TV and mark in isometric, similarly
get other new points in isometric.
• Darken the visible edges to complete
the isometric view.
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11. Tips to draw Isometric
View/
Projection
• Draw the TV and FV of the solid and are used to
complete isometric view/projection. But it is not
compulsory to draw TV & FV, box can be directly
constructed to draw the isometric view/projection.
• Hidden lines used for invisible edges are not
drawn in isometric view/projection.
• In isometric view/projection, marking and
dimensioning may be omitted and the drawing
of the three dimensional object is shown clearly
by using dark lines for visible edges.
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12. 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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13. End of Lesson 11
Thank You
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