Thread plug gages are fascinating products when you consider the technical details that go into their manufacture and the precision they embody. To some, they look like fancy bolts and are treated accordingly. To others who appreciate what it takes to make them, they represent a lot of precision for their low purchase price. The calibration of them presents similar approaches.
To the uninitiated it’s as simple as measuring the thread on a bolt. Those who know what they are doing understand there’s a lot more to it. In this column I’ll look at what is required to measure the most common elements of a thread plug gage.