As we use a lot of adjustable thread rings where I work, I have often pondered this question. I am the lead calibration guy, so I am the one doing the adjusting. So far, I have not found a good way to quantify the amount of adjustment made. We have gone to using mostly hilo type set plugs to take out some of the operator "feel" that is required when using truncated set masters. This provides us with more reproduceable results, but still does not address the question of "How far out was it?"
The best I've been able to come up with is to calibrate the hilo master, recording the measured size of both the hi and lo sections. Then, if the ring stops on the lo, for example, I can know how far undersize it was. If it doesn't stop on the hi section I can know that it is at least that amount oversize. Unfortunately, with an adjustable ring, there's no way that I know of to measure the actual pitch and minor diameters.
One thing you need to be aware of, though, is that if you change vendors, most, if not all, of your adjustable rings will have to be reset because the new vendor will be using different set masters of slightly different size than the old vendor. I would recommend finding a vendor that has one of two things; 1. A very experienced thread ring guy or 2. Uses only hilo set masters. Without a very experienced thread guy (i.e. one that has been doing it for many years and does very little else) your chances of getting reproduceable calibration and resetting results are pretty slim.
