Here's what I always understood:
We are going to measure the thickness of a sheet of friction material - it is raw (soft) and has not been pressed yet. We decide to use micrometers - so we take a micrometer that is known to be calibrated, get three operators together, and have each operator (all using the same mics) to measure 10 spots three times each (3 operators, 10 samples measured 3 times each by each operator). Say we come up with an unnacceptable GR&R results - the variation in measuring results deems the METHOD unnacceptable. So - we decide that the micrometer is not repeatable or reproducable when dealing with non-inspection employees (skill level) because the "feel" of the gage is so critical when dealing with the soft material (it's too easy to squeeze). Now we have choices - do we limit the inspection of this characteristic to Inspection Personnel only? - or do we use perhaps a snap gage that anyone can use regardless of their skill level?
If you've verified the inspection method, any micrometer that is in calibration will be acceptable to use. It's not about this particular micrometer, and this particular micrometer and this particular micrometer - it's about using
a micrometer for measuring
this characteristic. Back when I used to do GR&R for automotive companies we did not do it for every gage - it's not really about the gage itself, but the type of gage (or measuring instrument) you've chosen for a particular characteristic and the ability for anyone who has to measure said characteristic will get the same measurement as the next person. Things may have changed...or maybe we were wrong back then - but our customers were happy.
