Your set up is ingenious; I like it. As far as measuring the part while it is still in the chuck, I was amazed at how well a Dozume guage workes. I bought some from Uncle Larry’s Watch Shop that were used and later found a brand new one for $10.00 from a company on Ebay that sells watch tools. I cannot remember the name of their online shop but they are in England. I also bought a set of excellant tweezers from them for $30.00 for the set. Since cutting a part with a graver is a cut and feel process, the Dozume calipers should tell you what you need to know ie. part a little over size, take a little off. They are very repeatable so you can calibrate the diameter you want for your finished part with feeler gauges.