Rich: Thanks for the suggestions.
1. Yes, spindle feedback was checked.
2. Checked spindle speed averaging. This made no difference. Spindle speed readout was as erratic as before.
3. Ports & Pins, Index. Checked Active Low. This made no difference. Spindle speed readout was as erratic as before.
4. Plug in control. Nothing is checked but I did get a picture of myself.
5. Yes, I have M3 in my setup lines.
I am amazed that nothing changed, especially when putting on spindle speed averaging.
I take it from your suggestions that you feel this is a Mach3 issue and not a hardware issue?
Thanks.