Mill-Turn threading

[Nick]

Sorry for the daft question but I'm just started playing with diy cnc. Can I use mill as lathe using G32 or G33 for threading? Fusion postprocessor for Mach3 turn generated the code but the program just stop when hit the row with G32. Mach3 user manual doesn't mention those g codes at all.

[DaveCVI]

Hi,
I don't think mach3 has a G32 or G33. I believe that post will need to be changed to work with Mach3.
FYI, I never had much luck with using mil-turn to thread. Mach3 usually relies on an index pulse for sensing threading RPM (which my mill has) but I found that was not enough to make a good thread. The speed would vary and not be noticed by mach for several revolutions, by which time the thread was already ruined.
Dave

[Nick]

Hi Dave,
I've got spindle RPM feedback on my mill and the postprocessor is for Mach3 turn.I can create another profile for Mach turn but then how I can adjust the Y axis? What cycle you used for threading?
I've wached few videos for MSM mill-turn but couldn't see any threading.

Thanks,
Nick

[DaveCVI]

well, I remember never making a mill-turn threading video as I never managed to make a good thread on the mill.
The problem is that Mach3 only knows about an index pulse for measuring spindle speed. That lets mach measure the speed of the spindle (at best) 1/revolution. Mach appeared to take several revolutions to learn that the speed needed to be adjusted, then it takes some more time for that adjustment to happen etc. The feedback loop had too much latency in it to work well.
I also don't get super precise speed control from the VFD that runs the spindle. Perhaps if one has a massive spindle where the rpm never varies, mach might work for threading. At the time I did the mill-turn software, the mach forums for people threading on a lathe with mach3 were 50/50 as to success. I concluded that to thread I really needed a spindle encoder and a software base better than Mach3. I essentially wrote off the idea of threading (and rigid taping) with mach3.