Question

What is mean clearance?

(a) Maximum size of hole minus maximum size of shaft

(b) Minimum size of hole minus minimum size of shaft

(c) Mean size of hole minus mean size of shaft

(d) Average of both size of shaft and hole

This question was addressed to me in class test.

This intriguing question comes from Tolerances in section Limits, Fits and Gauges of Engineering Metrology

Answer 1

The correct answer is (c) Mean size of hole minus mean size of shaft

Best explanation: Statistical approach allows wider tolerances compared to complete interchangeability approach. Methods used by statistical approach are usually permits cheaper production.  Mean clearance is equal to (mean size of hole – mean size of shaft).