Thanks to Êostre I had time to finally fix the jaws on my #lathe chuck. I was going to grind them in place, as seen on the internet, but with the size of this wee boi it was too difficult. Also, fitting the Dremel to the cross slide rigidly enough proved to be more work than it was worth. In the end I just took the jaws out and hand-ground them, recursively checking for runout as you do with a 4 jaw chuck. Ended up with less than 0.02mm and no bell-mouth which will do me fine.
Yes, that's a socket wrench because a proper test bar would cost more than the lathe did. #ShedEngineering #crapMetrology #machining