Question

What is the relation between the effective diameter of a thread hole and an effective diameter of the screw in screw thread gauge?

(a) minimum effective diameter of a thread hole must necessarily be greater than the maximum effective diameter of the screw

(b) maximum effective diameter of a thread hole must necessarily be greater than the minimum effective diameter of the screw

(c) minimum effective diameter of a thread hole must necessarily be lesser than the maximum effective diameter of the screw

(d) maximum effective diameter of a thread hole must necessarily be greater than the minimum effective diameter of the screw

The question was asked in an interview for job.

This intriguing question originated from Gauge Wear topic in division Metrology of Screw Thread, Gauges for ISO Metric Screw Threads of Engineering Metrology

Answer 1

The correct option is (a) minimum effective diameter of a thread hole must necessarily be greater than the maximum effective diameter of the screw

Explanation: The minimum effective diameter of a thread hole must necessarily be greater than the maximum effective diameter of the screw. The pitch diameter (often called the effective diameter) of a parallel thread is the diameter of the imaginary co-axial cylinder which intersects the surface of the thread in such a manner that the intercept on a generator of the cylinder.