Mach does support G84 motions BUT it does not sync the Spindlle to the Zfeed. IT may be possible but i will not let that cat out of the bag.
A servo spindle can be refhome back to the index mark to set the Spindle to 0.000.
An M84 can be created to create a rigid tap function. It can have 3 outside param calls P,Q,R to set inside variables. The sequence can be done as a SUB so it SHOULD be able to simulate the G84 function quite easily.
Crusty OLD Machinist (;-)

? I resemble that remark a great deal (;-).
I can shuffle some more room on the page so IF you get time send me what you have code wise for what you do. I will look it over and see what we can do with it. Top secret of course(;-)
Single point threading THE HOLY GRAIL. IT all depends (;-), we will just throw it all in the frying pan and see if we get fried fish.
(:-)TP