Studs

The essentials

A stud is a cylindrical rod threaded at both ends, with no head. One end, the metal end, is screwed tightly into a tapped hole in one part; the other end, the nut end, passes through a clearance hole in the second part and receives a nut. A stud is used when a through bolt cannot be fitted, for example when one part is too thick, or when a cover must be removed often without damaging the threads in the main body. The stud stays in the body, and only the nut is removed.

Key points

• Plain stud: threaded at both ends with a plain (unthreaded) portion in the middle.
• Square-neck stud: has a square portion next to the metal end, so it can be gripped with a spanner and screwed into the tapped hole.
• Collar stud: has a collar formed on it which acts as a shoulder resting on the surface of the body, giving firm seating and a definite projecting length.
• The length of the metal end depends on the material: shorter in strong materials such as steel (about D), longer in softer materials such as cast iron.
• Typical use: holding the cylinder cover of an engine to the cylinder body.
• Sketching: draw the threads conventionally, show both thread ends, and keep the plain portion and any neck or collar in proportion.

Exam tips

• Remember the purpose of each stud feature: square neck for gripping, collar for seating.
• In situation questions, choose a stud when frequent removal of a cover is expected.

Common mistakes

• Drawing a head on a stud.
• Confusing the metal end with the nut end; the metal end goes into the tapped hole.