What's this tool?

[Sasquatch]

Then I'm guessing you shave a little off, test fit, shave some more, test fit, more, test, more test, until you get the fit.

In my case, yes, and that's why the jig is just a push-fit - I can pop the stem out in 1 second, and remount it identically in 1 second. It comes off probably 10 times as I get near the diameter I want, and I just cut it for the desired amount of friction on any given pipe. But then I am a pipemaking genius cyborg superman, so keep that in mind.

[pipedreamer]

You can take a box wrench and sharpen the top or longer tine. cut the other end off and epoxy it into a 1 foot long 1 inch diameter piece of dowel rod. This will make a tenon turning tool that lasts a long time. You can have it in several sizes. works well. I stole this from a wood turner a long time ago that couldn't use his hands well from being disabled.You use your other chisels to bring the size down first. Works every time and clean.