Detailed step wise explanation with hand sketches

1. Isometric Projection of
Frustum of a Cone
Drawing Steps By:
SUBIN B MAROSE
Assistant Professor
Department of Mechanical Engineering
PH: 9048572058

2. Question
• Draw the isometric projection of a frustum of
cone with base diameter 60 mm, top base diameter
35mm and axis length 50 mm.

3. Step 1
• Draw the top and front view of the solid in true
dimensions.

5. Step 2
• Mark the dimensions.
• Enclose the bottom circle inside a box and name it
1-2-3-4.
• Similarly enclose top circle in box 5-6-7-8.

7. Step 3
• Draw the isometric axes and plot point 1.

9. Step 4
•Important to take conversion factor=
0.816 since it is isometric projection.
• Note the length 1-2 which is 60 mm and plot its iso
length = 60 * 0.816 = 48.9 mm onto the isometric
axes.

11. Step 5
• Complete the box 1-2-3-4 in iso length.

13. Step 6
• Base circle will be represented as an ellipse which
we have drawn in several questions before.
• In this question, steps of drawing ellipse are not
repeated but it is visually represented.
• Any doubt, refer previous questions.

18. Step 7
• Draw a vertical line of height = iso height of
Frustum = 50 * 0.816 = 40.8 mm at point 2.

20. Step 8
• Similarly draw similar vertical lines from other
edges of the box.
• Join the end points of the lines.
• Name the top box also as 1-2-3-4 to avoid
confusion.

24. Step 9
• Now focus on top view.
• From point 6, draw a horizontal line and name the
meeting point as 'm'.
• From point 6, draw a vertical line and name the
meeting point as 'n'.

26. Step 10
• Lengths of 6-m and 6-n are equal here = 13 mm
• Plot the iso length of 6-m and 6-n = 13 * 0.816 =
10.6 mm onto edges 2-3 and 1- 2 respectively.

28. Step 11
• Draw parallel lines from points 'n' and 'm' as shown
in next slides.

31. Step 12
• You can complete the top box as shown in next
slide by taking similar dimensions.
• Name the box 5-6-7-8 which now you have created
and it is the isometric projection of the box 5-6-7-8
we have drawn in top view.

33. Step 13
• Since top of Frustum is also a circle, it will be seen
as an ellipse in the isometric projection.
• So we have to draw an ellipse in the box 5--6-78.
• Repeat all the steps we followed for drawing the
base ellipse.
• Refer the coming slides.

40. Step 14
• Join the top and bottom ellipse as shown
tangentially.
• Highlight the figure as shown.
• Please make sure that you darken the lines only at
the end.

43. Comments
• It is Isometric Projection.
• So take conversion factor.
• Draw lightly.
• Darken the figure only at the end.
• Practice and learn.
• Please feel free to rectify the doubts.

44. • End of presentation...