I had posted this, worded differently, some time back and didn't get any solutions so I'll try again.
Used ST-30;
Under load I get a LOUD, hi-pitched whine from the spindle. I have to plug my ears if I walk past the cooling fan area at the spindle end of the machine.
It seems fine under minimal load like a fine finish cut but even a .05 deep roughing cut at F.015 in our aluminum wheel centers brings the ear shattering whine. (1800RPM. .050DOC F.015)

Ideas?

JohnF
Phoenix.