What is valve lapping and how it's done

What is Lapping? | How Lapping Works? | slidingmotion

SOLVED: A lapping process which is used to grind certain silicon wafersto proper thickness (100 mil) is acceptable only if s, thepopulation standard deviation of the thickness of dice cut from thewafers, is at most 0.50 mil. Use a= 0.05 level of significance toestablish the confidence level of variance.

Lapping A Rifle Barrel - Shooting Times