Butch, I have worked in the machining trade for over forty years, building lots
of things, that people thought were not possible. I have made a lot of neck finish tooling for plastic bottles, with tolerances of "plus a half, minus nothing"
on a Harrison M350, with 2 axis readouts.
I am making no statements about anyone's abilities, but I feel that the comment about boring a die, on an engine lathe, was an accurate one. It was not said to be impossible, only difficult. A lot depends on the degree of accuracy that you can verify, not that which you can estimate, or assume.
I would agree that boring would improve concentricity, but the setting of the compound angle to the degree of precision needed to get the dia. at the
base of the die, and the shoulder, to both come to +/-.001", is not "easy".
A slight error in setting the tool height, will put you out of the game.
Butch, I have seen photos of your work, and I am impressed.
Regards,
Bob