meincer,
I have the punniest lathe of all, such that the speed will change as the cut gets deeper. Very nice for testing
threading though.....
Mach will vary the Z axis speed dependiing on what is happening with the spindle speed. It will not allow the Z to increase beyond what the code sets max rpm at. It will slow the Z movement down only to some % of the rpm.
Backlash compensation works fine in threading. If you use one of the wizards it will tell if you are exceeding the motor velocity defined when you did motor tuning, you can then modify rpm accordingly IN THE WIZARD and also set the spindle rpm (manualy in my case).
You can dry run and watch what is happening in the diagnostics ( barely visible box right under FILE) or the Plug In Control>lathe turn diagnostics. Use it to watch for change of G94 to G95, rpm, etc.
In config>ports & pins> spindle setup / special functions, check "use spindle feedback in sync mode" and
also spindle speed averaging if your using a slotted disc.
Hope this helps,
RICH