Some questions to JAZZCNC or any other closed loop stepper experts

[Muzzer]

.....I don't know what the real torque is at 2280 rpm, which is what the rpm is now when the chuck runs at 380 rpm, but it is enough to drill in steel.

Sorry, I hadn't twigged that you were planning on using this motor for the SPINDLE drive. That's probably not the best idea if I have understood what you are planning. I'd seriously recommend you use a proper VFD rather than a stepper or servo drive, which are intended for position control, rather than speed control.

Forgive me if I've got the wrong end of the stick here. I have no desire to criticise so much as help you avoid disappointment. Perhaps Jazz or someone else will dive in here, in the interest of constructive advice.