nic wrote:

clean-up pass is .005 or so and at 300+ rpm. But obviously,
it isn't really possible to make a full speed threading cut
up to a face,

If your lathe does _not_ have a screw on chuck, you can put the tool on
the back side of the work and run in reverse. That way, you cut away
from the shoulder and can cut at any speed you desire.

Ted