Jawaharlal Nehru Technological University Hyderabad B.Tech II MACHINE DRAWING AND COMPUTER AIDED GRAPHICS Previous Question Paper (July/August - 2021 - R13)

For a bolt of diameter (d) = 20 mm and length (l) = 85 mm with a square head, the following proportions based on the nominal diameter d are used for drawing:

• Width across flats (W) = 1.5d + 3 mm = 33 mm
• Head height (H) = 0.8d = 16 mm
• Nut height (Hn) = 0.8d = 16 mm
• Chamfer radius (R) = 1.5d = 30 mm

The two views required are the front view (elevation) and the side view (plan). In the front view, the bolt head is represented as a square of side W = 33 mm and height H = 16 mm. The shank of the bolt, with diameter 20 mm and length 85 mm, extends from the head. The threaded portion is typically taken as 2d + 6 mm = 46 mm, indicated by a thin line representing the core diameter. The nut is shown assembled on the threaded end with a height of 16 mm. In the side view, the square head appears as a square with chamfered corners, and the shank and nut are represented by concentric circles of diameters 20 mm and 33 mm respectively.

For a cotter joint with a sleeve connecting two shafts of diameter d = 40 mm, the design proportions are based on the standard empirical relations:

1. Diameter of the sleeve (D) = 2.5d = 100 mm.
2. Diameter of the sleeve at the cotter (D1) = 1.25d = 50 mm.
3. Length of the sleeve (L) = 3d = 120 mm.
4. Length of the cotter (l) = 4d = 160 mm.
5. Width of the cotter (w) = 1.25d = 50 mm.
6. Thickness of the cotter (t) = 0.3d = 12 mm.

To draw the half-sectional view from the front:

1. Draw the center line of the two shafts aligned horizontally.
2. Draw the two shafts of 40 mm diameter meeting at the center with a small clearance gap.
3. Draw the sleeve as a hollow cylinder of 100 mm outer diameter and 40 mm inner diameter centered over the junction.
4. In the front view, show the top half in section by hatching the sleeve and the cotters, while leaving the bottom half in full view.
5. Represent the cotters passing through the sleeve and the shafts at both ends. Use 45-degree hatching lines for the sectional parts of the sleeve and the cotter.
6. Ensure the taper of the cotter (typically 1:30) is indicated in the drawing.

The half-sectional view effectively displays the internal assembly of the shafts, the sleeve, and the cotters while maintaining the external profile of the joint in the lower half.