JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III MACHINE DRAWING AND COMPUTER AIDED GRAPHICS Previous Question Paper (September - 2021 - R18)

A tap bolt is a fastener that passes through a clearance hole in one part and screws directly into a threaded hole in the second part to clamp them together. It has a head at one end and threads at the other. In contrast, a stud bolt is a headless rod threaded at both ends. One end is permanently screwed into a tapped hole in the base component, while the other end passes through a clearance hole in the mating part and is secured with a nut. Stud bolts are preferred for assemblies requiring frequent dismantling to avoid wear on the tapped threads of the base component.

Conventional representation of screw threads follows standard engineering drawing practices where the crests are represented by thick continuous lines and the roots by thin continuous lines.

For a Square thread (nominal diameter 20 mm, pitch 3 mm): The profile is drawn as a series of squares. The distance between consecutive crests is the pitch (3 mm). The depth of the thread is half the pitch (1.5 mm). The crest lines are drawn as thick lines, and the root lines are drawn as thin lines connecting the squares.

For a Metric thread (nominal diameter 12 mm): The outer diameter is represented by a thick continuous line (12 mm). The inner (core) diameter is represented by a thin continuous line, typically calculated as approximately 0.85 times the nominal diameter. The thread ends are marked by a thick continuous line perpendicular to the axis, and the chamfer at the end of the bolt is drawn at an angle of 30 degrees.