Question

If the threads are cut on the internal surface of a hollow rod, these are known as

(a) internal threads

(b) external threads

(c) helix

(d) none of the mentioned

I had been asked this question by my school teacher while I was bunking the class.

The origin of the question is Friction of a Body Lying on a Rough Inclined Plane in section Friction of Machine Kinematics

Answer 1

Correct answer is (a) internal threads

The best explanation: The fastenings have screw threads, which are made by cutting a continuous helical groove on a cylindrical surface. If the threads are cut on the outer surface of a solid rod, these are known as external threads. But if the threads are cut on the internal surface of a hollow rod, these are known as internal threads.