Bridgeport VMC 760/16 Spindle Repair

The Bridgeport VMC 760/16 is a CNC vertical machining center.  It comes standard with a grease lubricated and belt driven spindle capable of running up to 6,000 rpm.

CHALLENGE

Upon inspection of this Bridgeport VMC 760/16 spindle, we found that the front bearings were installed wrong (backwards).  The rear roller was found to be not loaded properly and the hydraulic nuts were made wrong and not functioning properly. We then measured the critical dimensions and found a few issues to be addressed.  First, the shaft taper had 50 microns run out.  Second, the front journal had 37 microns out.  Third, the front and rear bearing shoulders had 15 microns run out.  Lastly, the tail of the shaft had significant run out as well.  We also noted that the rear housing was oversized.  Lastly, there was a dremmel cut in the hydraulic nut area of the shaft and the rear bearing was spinning in the housing.

SOLUTION

The following actions were performed on this Bridgeport VMC 760/16 spindle:

• Replace bearings, bellevilles, o-rings, and assembly screws
• Grind, chrome plate, and finish grind (GPG) the rear housing and taper
• GPG the journals and shaft tail
• Kiss grind bearing shoulders
• Machine and finish grind new front hydraulic nut
• Custom grind rear hydraulic nut to fit shaft

RESULT

After reassembly of all components, adjusting bearing preload, and undergoing break-in and testing procedures, this spindle passed our final quality inspection before being returned to our customer with a 1-year warranty.