Re: How to keep gage block sizes unknown for R&R factors of MU
Hershal, and to other metrologists
In regards the .00005" uncertainty contribution of wringings...
If this uncertainty contribution can be applied to the measurand, is the same contribution applicable to the measuring equpiment, in other words to the wring between the measurement anvil and the gage block surface?
I've often wondered about this when calibrating Mitutoyo and various Chinese off-brands which have extremely flat anvils. When I apply constant pressure and repeat measurements, the micrometer will come down and make contact, reading about +.0001, and then seat down right onto target. It seems like the anvil meets a film of surface tension and that it takes longer to push this air from between the anvil and the gage block. This may not be what I'm observing but it's very convincing!
In the case of this one wringing (since the .100 gage block is stuck to the bottom anvil) I could certainly see an expanded uncertainty of +/- .000029 being applied to the final measurement.
The question that raises in my mind applies when I'm measuring a stack of 2 blocks with a plain anvil micrometer, 4 wringings. The uncertainty contribution due to gage wringing, 4 x .00005, expanded uncertainty .000115". Is this reasonable?
How can this be reduced? For assessing calibration technicians, I think a total uncertainty of that amount would be large. Using just one block lets the operator know exactly what number to come up with.
It's hard to take an assessment of a person's skill and not know precisely what you're doing to measure it.
I will of course be doing research, but I will watch for a response.