[carbidecraters]

I have a quickturn 10 mazak lathe with a mitsubishi controller and the spindle is erratic and will jerk but the bearings have been replaced. Anyone here know much about them? Mitsu said it would be $2500 to look at it.....help!!!

[Al_The_Man]

Is it a DC spindle motor? if so, check the tach.
Al.

[carbidecraters]

hmmm not sure if it is a DC it has 440 3 phase piped in so I doubt it

[Al_The_Man]

If its a mazak/Mitsubishi it is either going to be a controlled DC spindle or an AC spindle, not likely to be standard induction motor.
disconnect the drive belt if it has one. If AC spindle, there is a inductive ac tach on the rear of the motor consisting of a toothed wheel and a pick-up with a small box above it with a small circuit board with about 4 pots in it, this can cause erratic behaviour if defective or mis-adjusted, it requires a double beam 'scope to align it, I should have the information sheet if needed.
If DC motor, it is just a straight forward DC tach and may need cleaning.
Al.

[carbidecraters]

AL any schematics you can send me please do...I will look into it further

[Al_The_Man]

Can you identify wether AC or DC? There should be a motor label or if the motor itself has brushes then its DC.
Al.