Re: Bad face mill finish. Profile is perfect
If the tool holder is not pulling in tight to the spindle bore, the tool holder would flop around in the spindle taper a bit and you would be able to see some lateral movement in the toolholder and it would probably chatter like crazy when cutting. You could have a belleville washer problem and may need to change them out, but from what you said, that does not seem too likely. This sounds like a mechanical problem rather than a resolver issue.
My best guess is spindle bearings, especially if you can move the spindle relative to the head. Backlash in the Z ball screw could also be the problem. You need to make some measurements to find exactly where play is coming from.
Jim Dawson
Sandy, Oregon, USA