Northland Tool Blog
Mitsui Spindle Rebuild

Mitsui Spindle Rebuild

This spindle had been recently rebuilt by someone else before it arrived at NTE. It was running very hot and seizing in our customers machine. The heat was caused by too much grease in the bearings. This condition makes the balls of the bearings “plow” through the grease causing resistance and heat. This heat causes the bearings to expand and eventually the clearance between the balls and raceways disappears. This is when the spindle stops turning.

Possible cause of failure:
Front bearing #2 feels rough, all bearings have excessive amounts of grease.
Journal & housing fits are all within ISO.
Taper runout <2µ.

Recommended action:
Clean, inspect overall dimensions.
Replace bearings, seal & bolts.
Adjust preload, balance, assemble and break in. Final quality control inspection.