Bridgeport VMC 3020, 10000 RPM, grease bearing lubrication, belt driven
Not your typical NTE spindle rebuild
This spindle arrived at our facility after being completely disassembled by another rebuilder. Our customer told us that he had become frustrated when the quote was not provided for nearly a month. After consulting with the OEM, the customer decided to get the spindle into our hands for re-quoting.
In these cases it is never a simple task determining the cause of failure, especially when the spindle has significant damage to multiple components. The ID of the front hydraulic nut was worn to the point of being unable to grip on the spindle shaft, which allowed the front bearings to lose preload. The rear roller bearing had also suffered catastrophic failure. In both cases, the bearing journals & shoulders of the spindle shaft had also been damaged. In addition, the tooling taper of the shaft had excessive runout and one of the drive dog mounting screw holes was severely damaged. Finally, it was determined that the drawbar shaft was bent & twisted by >170µ, and the spring seating washer was missing.
Our usual comprehensive approach to spindle rebuilding would have made this repair cost-prohibitive, especially since our customer uses this machine for secondary operations. They asked us if we could find a way to provide a more economical repair while still offering our one year warranty. We were able to repair the front hydraulic nut by grinding, chrome plating & finish grinding the ID. The spindle shaft, drawbar shaft & spring seating washer were replaced with used components which we had recertified to fall within spec. We used all new components to replace the front bearings, rear roller, Bellevilles, gripper balls, seals, o-rings & assembly screws. We even upgraded the rear roller from a brass cage as found to a version with a phenolic cage which has a higher speed rating more appropriate to the top rated speed of this machine.
After our usual break in & final QC process, we were able to ship the rebuilt spindle back to our customer with less time spent in our facility than it took for our competitor to provide a quote. While we did not follow our standard protocol of rebuilding the spindle to “as new” condition, we did not cut any corners which would adversely affect the longevity of the spindle. Our customer reported to us that they have run multiple jobs and the spindle has performed as expected. They also expressed their appreciation for our responsiveness, quick turn-around and our ability to tailor a successful solution to their particular circumstances.