That is, if I set the pitch to 10.666667 TPI, .0938", the threads come out at 16TPI, .0625" .

seems too much of a coincidence your spindle ratio is set to 2/3
Hood

Dear God, if it really is that simple, I'll never live it down. I'll try it right now.

Dont worry about it being that simple, if it works just be happy

Hood

why would you have set the spindle pulley to .67 ??

Looks to have been the problem. Why would it have worked in the older version with a .67 ratio? Granted, I did have threads being wiped off for the last 2.5" of a 4.5 cut, but it was good up until the spring passes. Also, why is the spindle response slower in the xml i posted earlier vs the one I attached just now? This one nails the speed within a second and holds. The other starts slow and then gains and levels out.

Thank you so much for the help. Whenever there is a problem, you are usually the first to help. This board is lucky to have you.

Tim

why would you have set the spindle pulley to .67 ??

A combination of what my manual said, and that .67 is the motor to spindle ratio. It made sense in my mind, but I can see how it made a problem. Again, it DID work before at .67

Difference is you have averaging on now and didnt before.
Regarding the pulleys ratio, you would only use a ratio if the actual sensor was on the motor side rather than directly on the spindle.
Hood

sounds odd, but great it's now sorted.

One thing I always add to the threading wizard, is a pause for a couple of seconds on the first pass to let mach see the correct speed. You can set this in spindle setup if you like.

FWIW,
Mach compensates for changes in spindle rpm, slow down only, and adjusts the next pathing based on what the real time ( ie; it is not manipulating some reading and the shared time with windows ) rpm was, and averages it if spindle speed averaging is selected and as such then you have two compensations fighting each other, namely the vfd trying to maintain an rpm and mach trying to correct for a slow down of rpm. So the fix was to set rpm manualy and not have the problem. Frankly, good threading relies on enough spindle power being delivered to maintain the rpm and as you deviate from that threading results / accuracy will suffer. Frankly, if your spindle speed is solid spindle speed averaging dosen't do much for you.

Not sure if things have changed in later versions of MACH as i still use an older version......

RICH