Textbook of Engineering Drawing, Second Edition

_____ Development o/Surfaces 7.9

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A

A.

DEVELOPMENT

Fig. 7.9 Development of Frustum of Square Pyramid

1. Draw the two views of the given pyramid and indicate the cutting plane.


2. Locate the points of interseciton 11,21,31,41,51 and 61 between the slant edges and the cutting
   plane.


3. Obtain the sectional top view by projecting the above points.


4. With 0 as centre and radius equal to the true length of the slant edge draw an arc and
   complete the total development by following construction of Fig. 7 .8.


5. Determine the true length 0I21}, 01 3\, etc., of the slant edges 01 21, 0131 , etc.
   Note
   (i) To determine the true tength of the edge, say 01 21, through 21 draw a line parallel to the base,
   meeting the true length line o-a at 21}. The length 0121} represents the true length of 0121.
   (ii) 0111 and 0141 represent the true lengths as their top views (01, 04) are parallel to xy.


6. Mark 1,2,3 etc., along OA,OB,OC etc., corresponding to the true lengths 01 11, 0121 , 0^131 , etc.,
   in the development.


7. Join 1,2,3 etc., by straight lines and darken the sides corresponding to the truncated portion of
   the solid.

Problem: A cylinder of diameter of base 40 mm and height 50 mm is standing on its base on

HP. A cutting plane inclined at 45° to the axis of the cylinder passes through the left extreme

point of the top base. Develop the lateral surface of the truncated cylinder.

Construction (Fig.7.1 0)