JNTU B.Tech II MACHINE DRAWING Previous Question Paper (May-2019 - R13)

For plates of thickness t = 25 mm, the following design parameters are calculated based on standard empirical relations for a double-riveted zig-zag lap joint:

• Diameter of rivet (d): Using Unwin's formula d = 6.05 * sqrt(t), d = 6.05 * sqrt(25) = 30.25 mm. Adopt d = 30 mm.
• Pitch (p): For a zig-zag lap joint, p = 3d + 10 mm = 3(30) + 10 = 100 mm.
• Transverse pitch (pt): For zig-zag riveting, pt = 0.6p = 60 mm.
• Margin (m): m = 1.5d = 1.5 * 30 = 45 mm.
• Diagonal pitch (pd): pd = 0.33p + 0.67d = 0.33(100) + 0.67(30) = 53.1 mm.

In the sectional front view, show the two plates overlapping with a width of 3m + (n-1)pt. Draw two rows of rivets in the section. The rivets are represented with a snap head profile, where the head diameter is 1.6d = 48 mm and the height is 0.7d = 21 mm. Hatch the plates using thin lines at 45 degrees, but do not hatch the rivets themselves.

In the top view, draw the plates showing the overlap width. Mark the rivet centers in a zig-zag pattern. The first row of rivets is placed at a distance of m from the edge, and the second row is at a distance of pt from the first. The rivets in the second row are positioned at a distance of p/2 from the vertical centerlines of the first row rivets to create the zig-zag arrangement. Use center lines to indicate the pitch and transverse pitch dimensions.

A knuckle joint is used to connect two rods under a tensile load where small amounts of angular movement are required. For a rod diameter (d) of 25 mm, the standard proportions are used to calculate the dimensions of the joint components.

Key proportions for the design:

• Diameter of rod (d) = 25 mm
• Diameter of knuckle pin (d1) = d = 25 mm
• Diameter of pin head (d2) = 1.5d = 37.5 mm
• Thickness of eye (a) = 1.25d = 31.25 mm
• Thickness of fork (b) = 0.75d = 18.75 mm
• Outer diameter of eye (D) = 2d = 50 mm

The sectional front view is drawn by taking a vertical section through the center of the knuckle pin. This view shows the fork end, the eye end, the knuckle pin with its head, and the collar secured by a taper pin. The section lines are drawn at 45 degrees to indicate the cut surfaces of the fork, eye, and pin.

The top view is projected from the front view, showing the rod ends, the fork arms, and the circular profile of the knuckle pin head. The side view is drawn by projecting from the front view, typically looking from the left, showing the circular cross-section of the rods and the rectangular profile of the fork ends.