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 I'm having an odd problem. I'm running a threading routine using G76. I thought that, while threading, I could change the spindle speed without affecting the operation. Everything seemed to be working fine until I starting threading something a little larger for me - a 1"-8. I started to see bad gouging off and on during the threading. that at times nearly stopped the (7HP) lathe. I was only taking off about 0.002" per pass for most of the operation. I thought something must be moving, and checked all the obvious things. Everything looked OK.

One of the things I tried was making a scratch pass at three different speeds, 100, 150 and 200 RPM. I ran the same program each time without changing the setup. You can see that the cut indexed to a different point for each speed. Conversely, if I ran it three times at the same speed, it would index to the same cut.



This is not good! It means if I cut a thread and then need to recut it, I need to make sure that the spindle speed is exactly the same or I'll get a different thread position. Needing to cut the thread again can be because the piece rotated in the chuck during the cut or I didn't set the tool X position deep enough. I'm also thinking that as the lathe slows down slightly, it might change the Y position of the tool incorrectly and cause the gouging.

Any ideas?

Two indexing signals to LinuxCNC: one pulse per revolution for indexing, and ten pulses per revolution for position
Spindle speed set manually, and not by LinuxCNC
LinuxCNC v2.9.3

Hello PCW,

I debounced when using the 7i73 but without success.
I tried with isolated input on the 7i96s and it's working fine.
Do you have some documentation regarding the slow option? I find the input in Hal show but it's always low.

I'm very happy that it's working but I still don't get something. If it's due to the EMI, why I don't see the dot blinking in Hal show? It's strange...