Don, you mentioned using a diamond wheel. What would I use on my
lathe to turn down the diameter? From experience so far, a sharp point
turning insert does not work very well. Maybe I should try one of my
larger radius inserts.

Do they have any type of diamond impregnated abrasive material I can
use on a lathe? I am just throwing things out right now. I don't
really know what else to try.

I will look at the McMaster diamond tips tools. But the magnets or so
fragile, that if the tip of the tool catches any tiny imperfection, the
magnet breaks.

Thanks for all the info.