JNTU B.Tech II MACHINE DRAWING AND COMPUTER AIDED GRAPHICS Previous Question Paper (March - 2022 - R13)

To draw a square headed bolt of 30 mm diameter (d), the following standard proportions are used: Nominal diameter (d) = 30 mm, Width across flats (W) = 1.5d + 3 mm = 48 mm, Thickness of head (k) = 0.75d = 22.5 mm, Length of bolt (l) = 100 mm (assumed), Thread length (b) = 2d + 6 mm = 66 mm.

Front View: Draw the shank as a rectangle of length 100 mm and width 30 mm. At one end, draw the square head as a rectangle of 48 mm width and 22.5 mm thickness. Show the chamfer on the head by drawing arcs with a radius of approximately 1.5d, creating a curved profile on the top face. Draw the thread profile at the end of the shank using a thin line for the minor diameter (0.85d) and a thick line for the major diameter (d).

Top View: Draw a square of 48 mm side length representing the head. Inside the square, draw a circle of 30 mm diameter representing the shank. Draw an outer circle representing the chamfered corners of the head. Add a partial circle representing the thread root diameter.

Left Hand Side View: Draw a square of 48 mm side length. Project the shank diameter (30 mm) as a circle centered within the square. Represent the chamfered edges of the square head by drawing diagonal lines connecting the corners of the square to the inner circle.

For a double-riveted, double-cover plate zig-zag lap joint with plate thickness t = 15 mm, the following design parameters are calculated based on standard empirical relations:

1. Diameter of rivet (d) = 6√t = 6 × √15 ≈ 23.2 mm. Adopt d = 24 mm.

2. Thickness of each cover plate (t_c) = 0.625t = 0.625 × 15 ≈ 9.375 mm. Adopt t_c = 10 mm.

3. Pitch (p) = 3d = 3 × 24 = 72 mm.

4. Zig-zag pitch distance (p_z) = 0.6p = 43.2 mm.

5. Margin (m) = 1.5d = 36 mm.

6. Transverse pitch (p_t) = 0.8p = 57.6 mm.

The sectional front view shows the two main plates (15 mm thick) with two cover plates (10 mm thick) on either side. The rivets are arranged in two rows in a zig-zag pattern, meaning the rivets in the second row are positioned at the midpoint of the pitch distance of the first row. The cross-section is taken through the center of the rivet rows, showing the double-shear condition of the rivets.

The top view displays the edges of the cover plates and the main plates. The rivet heads are represented by circles of diameter 1.6d (approx. 38 mm). The zig-zag arrangement is clearly visible, with the centers of the rivets in the two rows offset by p/2 = 36 mm. The longitudinal edges of the plates are indicated by hidden lines where necessary, and the pitch and margin distances are marked to define the joint geometry.