We received the Okuma BT-40 Spindle with the complaint of excessive noise along with vibrations. Also the reported runout on a 300 mm test mandrel was more than 0.3 mm. The spindle was dismantled and all the components were cleaned. Bearing condition was found to be absolutely dismal. Spindle nose taper had bell mouthing shape.

Ground the spindle nose within the accuracy of 1 micron. All the rotating components were dynamically balanced. Then Spindle was re-assembled. Checked the runout which was 1 micron on the spindle nose and 8 micron on a test mandrel of 300 mm length.