Question

What is the formula for tolerance on effective diameter (D = major diameter, L = length of engagement, p = pitch, a, b, c are constants)?

(a) a∛D  +b√L  +c√p

(b) a∜D  +b√L  +2c√p

(c) a∛D  +b√2L  +c√p

(d) 2a∛D  +2b√L  +3c√p

I had been asked this question in an international level competition.

This is a very interesting question from Tolerance for Screw Thread Gauges and Screw Threads topic in chapter Metrology of Screw Thread, Gauges for ISO Metric Screw Threads of Engineering Metrology

Answer 1

Right answer is (a) a∛D  +b√L  +c√p

To explain I would say: Effective diameter tolerance depends on the Diameter, length of thread, pitch. It depends on them non linearly. Equation of tolerance is  a∛D  +b√L  +c√p where D = major diameter, L = length of engagement, p = pitch, a, b, c are constants.