Woody,
I'll fool with threading hopefully today and use V3.042.20. I want to test out the "PUNNY" lathe here anyway.
Can use the PP port or the SS, slow the spindle down, and with new steppers installed and backlash down to
.001 on the Z can now try threading at a variety of spindle speeds probably out to 1300 rpm.
I don't have an answer for you, but, just quickly dry running a few times, motor running and steppers disengaged i was able to see the DRO's change at rpm decreases of less than 5% and really go bonkers if you varied the
rpm at certain times of the thread cycle. I wouldn't put much credibility to the above as it wasn't done in a disciplined way. One thing I did notice though, was, that during the "threading" part of the cycle, if the spindle slowed down,...... the x axis didn't change / stayed at it's position.
Later,
RICH