JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II MACHINE DRAWING AND COMPUTER AIDED GRAPHICS Previous Question Paper (November/December - 2020 - R13)

To draw the schematic representation of an internal single right-hand V-thread with a nominal diameter of 50 mm and a pitch of 6 mm, follow these steps:

1. Draw two concentric circles representing the internal thread. The inner circle (minor diameter) has a diameter of 50 mm - (1.0825 × 6 mm) ≈ 43.5 mm. The outer circle (major diameter) is 50 mm.
2. In the side view, represent the major diameter with a continuous thick line and the minor diameter with a thin continuous line.
3. For the longitudinal view, draw two parallel lines representing the major diameter (50 mm apart) and two inner parallel lines representing the minor diameter (43.5 mm apart).
4. Since it is a right-hand thread, the thread profile should incline upwards from left to right.
5. Draw the thread crests using continuous thick lines and the roots using thin continuous lines.
6. Space the thread crests according to the pitch of 6 mm.
7. Indicate the thread start by showing the profile beginning at the end of the threaded portion.

A bushed journal bearing for a 50 mm diameter shaft consists of a cast iron body, a gunmetal bush, and a cap. To draw the sectional view from the front with the left half in section, follow these steps:

1. Establish the center line of the shaft at a height corresponding to the bearing center. Draw the shaft with a diameter of 50 mm.
2. Draw the gunmetal bush surrounding the shaft with a thickness of approximately 6-8 mm. The bush is typically flanged at one end to prevent axial movement.
3. Draw the body of the bearing, which houses the bush. The base is usually rectangular with bolt holes for mounting.
4. For the left half in section, apply cross-hatching lines at 45 degrees to represent the cast iron body and the gunmetal bush. Use standard hatching conventions: dense lines for the bush and wider spacing for the body.
5. Include the cap, which is secured to the body by studs or bolts. The sectional view should show the internal clearance between the shaft and the bush, typically 0.05 mm to 0.1 mm, though this is often represented schematically.
6. Ensure the section line passes through the center of the shaft and the bolt holes. The right half of the view remains in elevation, showing the external features of the bearing cap and the mounting bolts.

Key dimensions for a 50 mm shaft include a bearing length of approximately 75-100 mm and a base plate thickness suitable for M16 or M20 bolts.