Question

What is the relation between close fit and free fit?

(a) Close fit tolerance is one third of free fit

(b) Close fit tolerance is one half of free fit

(c) Close fit tolerance is two thirds of free fit

(d) Close fit tolerance is three fourths of free fit

This question was addressed to me by my college director while I was bunking the class.

My doubt is from Tolerance for Screw Thread Gauges and Screw Threads topic in division Metrology of Screw Thread, Gauges for ISO Metric Screw Threads of Engineering Metrology

Answer 1

Right answer is (c) Close fit tolerance is two thirds of free fit

To elaborate: The basic formula gives effective diameter tolerance for medium fit. Close fit tolerances are two-thirds of free fit, and free fit tolerance is one and a half times that of medium fit. This results in tolerance increasing by 50% each time from close-medium-free fit.