The term ‘proficiency testing’ is one that every accredited calibration laboratory is quite familiar with. In basic terms it refers to a method of evaluating how well a laboratory is doing a particular calibration with respect to its claimed measurement uncertainty and how it fares with other participants.
If you’re having problems with thread measurements but the answers you’re getting from your usual sources aren’t solving them, it’s natural that you would try and get some unbiased advice from a specialist.
These two choices for bore measurement come into play when close tolerances are the order of the day and speedy, repeatable measurements are required in a production environment. Keeping these requirements in mind, instrument makers usually offer options such as hard chromed bodies or carbide pads and contacts where needed to keep wear at a minimum.