It has been my experience that Mach need to know the exact position (angle) of the spindle.
They specify a certain width of the "window" for an optical sensor in order to set up timing for the pass. Also the ability of the Z axis to accelerate is important, to that end I place the start of the thread about .100" before the actual material to be threaded.
Several years later I find my self still reading and re-reading the Mach manual and groping for answers at times. A bit like witchcraft!! LOL!
Good luck!
“ In questions of power, let no more be heard of confidence in man, but bind him down from mischief by the chains of the Constitution.” Thomas Jefferson