Hitachi Seiki HT-250 Spindle Repair

Possible cause of failure:
Customer stated that the rear bearing is bad and was vibrating at 1,500 rpm.
Rear roller bearing may not have been preloaded correctly. Rear roller housing bore and shoulder have pre-existing damage from someone trying to remove the rear roller outer race. It is oversized +3/+7
(iso is +2/-18)
Front housing is oversized +20/+30 (iso is +/-10)and has pre-existing damage.
Rear jacking screws for removing the outer race are broken off and stuck.
Shaft lathe taper and face could use a cosmetic kiss grind.
Light damage to front cover.

Repair action:
Clean, inspect overall dimensions.
Grind, chrome plate and finish grind the front and rear housing.
Kiss grind lathe taper and face.
Replace bearings and o-rings.
Stone out damage on the front cover.
Install 4 new jacking screws in rear housing shoulder for outer race removal.
Adjust preload, balance, assemble and break in. Final quality control inspection.



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