thread mill programme without G42

Are you referring to a canned tapping cycle. If so, it is a machine calculated feed and speed that inserts a cutting tool into a hole at center. This is done with a tap typically.

My memory is fading on my g-codes but your 41 & 42 are inside outside comps if not mistaken. Or are those clock/counter clock? Damnit. coolant on/off? No?

Want to use my Mazatrol?

cr3

G41 and G42 are the offset direction. For a straight infeed the g codes will cancel if the offset value is Zero.

If your control will only do helical threading then you might try using a tapping head. Calculate your feed rate by using the TPI and spindle speed. Set your feedrate one to two threads slower, reverse the spindle and feed out. This has worked for years.

Toolmaker