Question

What is the virtual change of effective diameter of bolt or nut in case of whitworth thread in terms of error in flank angle?

(a) 0.1921 X p(θ1 + θ2)

(b) 0.182 X p(θ1 + θ2)

(c) 0.0195 X p(θ1 + θ2)

(d) 0.0105 X p(θ1 + θ2)

I got this question during a job interview.

Asked question is from Effect of Pitch Errors in chapter Metrology of Screw Thread, Gauges for ISO Metric Screw Threads of Engineering Metrology

Answer 1

Correct option is (d) 0.0105 X p(θ1 + θ2)

To explain I would say: A Corresponding reduction in the effective diameter is also needed for the errors in flank angles, if the screw or nut is to fit a perfect ring gauge of the same nominal size. Formula for virtual change in effective diameter is : 0.0105 X p(θ1 + θ2). Where p is the normal pitch and θ1 and θ2 are the error in flank angles.