Question

What is the symbol designated for the pitch diameter combination of an ISO Metric screw thread by IS: 4218 (Part II)-1976?

(a) M

(b) PD

(c) DP

(d) P

This question was addressed to me in an online interview.

The origin of the question is Diameter and Pitch Combinations topic in chapter Metrology of Screw Thread, Gauges for ISO Metric Screw Threads of Engineering Metrology

Answer 1

Correct choice is (a) M

The explanation: According to this IS: 4218 (Part II)-1976, the pitch diameter combination of an ISO Metric screw thread is designated by the letter M followed by the values of the nominal thread diameter and the pitch(expressed in mm).