JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II MACHINE DRAWING Previous Question Paper (July/August - 2021 - R13)
Answer any Two questions from Part-A
Part-B is Compulsory
Part A
Draw sectional front view and top view for a double riveted lap joint with zigzag riveting. Take plate thickness as 16 mm.
Answer
For a plate thickness (t) of 16 mm, the design calculations for a double riveted zigzag lap joint are as follows:
1. Diameter of rivet (d): Using Unwin's formula, d = 6.04 * sqrt(t) = 6.04 * sqrt(16) = 24.16 mm. Adopt standard rivet diameter d = 24 mm.
2. Pitch (p): For zigzag riveting, p = 0.6 * d + 4 * t (approx) or commonly p = 3 * d = 72 mm.
3. Transverse pitch (pt): For zigzag riveting, pt = 0.6 * p = 43.2 mm (or minimum 0.8 * d = 19.2 mm, typically 0.8 * p = 57.6 mm).
4. Margin (m): m = 1.5 * d = 36 mm.
The sectional front view shows the two plates overlapping with two rows of rivets. The rivets are arranged in a zigzag pattern, meaning the rivets in the second row are placed at the midpoint of the pitch distance of the first row. The cross-section reveals the rivet heads (snap heads) and the plate edges. The top view shows the two rows of rivets with centers offset by p/2, illustrating the zigzag configuration. The section line should be drawn through the center of one row of rivets to show the internal details of the joint clearly.
Sketch the conventional representation of the following:
External threads
Answer
For external threads, the crests (major diameter) are represented by a continuous thick line, and the roots (minor diameter) are represented by a continuous thin line. In the end view, the crest is a complete circle (thick line), while the root is a three-quarter circle (thin line).
Internal threads
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Thread in section
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Assembled threads in section
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Draw the sectional front view and top view of a knuckle joint to join shafts of each 25 mm diameter.
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Draw two views of a Foot step bearing for a shaft 100 mm diameter.
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Part B
Assemble the parts of the milling machine tail-stock, shown in figure and draw:
sectional view from the front
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view from the right. All the dimensions are in mm.
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