Question

Which of the following is periodic pitch error?

(a) Successive portion of thread is longer than the mean

(b) Successive portion of thread is shorter than the mean

(c) Successive portion of thread is longer or shorter than the mean

(d) Successive portion of thread is neither longer nor shorter than the mean

I had been asked this question by my college director while I was bunking the class.

I'm obligated to ask this question of Effect of Pitch Errors topic in section Metrology of Screw Thread, Gauges for ISO Metric Screw Threads of Engineering Metrology

Answer 1

Right option is (c) Successive portion of thread is longer or shorter than the mean

Easiest explanation: Periodic pitch error repeats itself along the thread at regular intervals of time. In this type of error, successive thread portions are either shorter or longer than the mean. It occurs when the tool velocity work ratio s not constant.