Got my spindle motor tach generator installed and working well which now gives me a very steady spindle speed.  Steady enough that I'm ready to try some threading

 I did some dry runs last night and when I grab the chuck in my hands to slow down the spindle a little, I can hear the Z stepper slow down & speed up when I release it; so far so good!

I'm sure there's going to be a lot of cut & try until I get more familiar with things.  When the threading cycle finishes & the spindle shuts off, does the Z stay indexed to the spindle?  In other words do I have to "pick up" the thread again if I find that it's a bit too large and I have to go back & shave off a bit more....or does Mach remember where it was and stay synced up so it runs right back down the thread exactly so all I have to do is dial up a bit deeper cut?

EDIT: Sorry, should have said I'm using the PP with an optical sensor with single slot on the spindle.

As long as you do not remove the part from the chuck and your code starts from the same Z position you can alter the X min dimension and run again no problem.
Hood

Thanks Hood, one less thing thing to worry about!