Spindle Step/Dir servo ramp down before stop on M stop command.

FF1=1 assumes the steps/turn=encoder counts/turn. Is this not the case?

That is the first time I have had that explained! I have not found that definition anywhere..

When you say steps/turn do you mean spindle servo motor steps/turn?
They are different - motor steps = 8000steps/rev. Encoder is 1024 lines=4096 edges/rev. ( which is 4096 encoder counts correct?)
This was setup in the original Pncconf where I did the 'scale' setup for spindle. Spindle RPM does read correctly when running in spindle mode, so encoder is set correctly, as is step pulse rate for that rpm.

PCW wrote: Do you clear the encoder before changing to C axis mode?

My concern with that idea is that it might mean that the system does not pass through the index and reset to true zero.

I had assumed that no matter how huge the initial error, once the spindle index cleared the error would be no more than half a turn.

If this was my own machine, by now I would be done with "simple" and be writing a custom HAL component.

So is the C axis re-homed when changing to AXIS mode?

PCW wrote: So is the C axis re-homed when changing to AXIS mode?

That was the idea.

Partly based on my first LinuxCNC lathe that would lose counts at max spindle speed, though that really shouldn't be an issue here. I really need to learn to trust encoders

Maybe we should use the orient component after all?

I have nowhere near the ability to do anything like that - I don't even have a sound understanding yet of how what you have implemented actually works Andy.
I don't know and cannot find how the encoder/reset/index mechanism works when switching between modes.
I did post about 5 or 6 posts previous all the parameters I looked at with halmeter, etc, but need guidance in that as I have no idea..
There are also the jog issues I raised in those posts, and I have really tried and searched to find the reason for that too.

Chaps, if this is becoming bothersome and a burden, please say so and I will cease and desist..I cannot fix the current issues and I am not able to simply rewrite a solution in HAL - if I could I would have done so long ago instead of floundering in the wings, trying my best to learn!
Simply beyond my ability with my present knowledge.

Thank You