"Proctologically Violated©®" wrote:

Still, iof he used a hand-operated wrench on the drawbar, didn't he FEEL
something going wrong when he tightened it?

Another good observation.
This is a very very talented old-school machinist (if not a little odd), who
often works behind various shleps in his employ.
He proly should have noticed, but when you perenially exist in the line of
financial gunfire, **** happens in the heat of battle. This is one of them.

Likely when the end of the draw bar threads entered the collet insert, he experienced
galling. It is amazing how galling can totally jam a fastener.

Wes