Brother TC-229N Spindle Repair

The Brother TC-229N is a high production CNC vertical machining center.  It comes with a grease lubricated and coupling driven spindle capable of running up to 10,000 rpm.

CHALLENGE

This Brother TC-229N spindle arrived as a bare shaft and bearings.  Upon inspection, we noted that the bearings had failed from coolant contamination.  The grease was washed out of both the front and rear pairs.  In particular the #1 front bearing cage was broken and debris from it contaminated the rest of the bearings.  We then measured the critical dimensions of the spindle and found a few issues to address.  First, the 50mm front bearing journal was undersized -7/-9µ (ISO is ±4µ), bearings will fall off the shaft.  Second, the 40mm rear bearing journal was undersized -6/-10µ (ISO is ±3.5µ), bearings will fall off the shaft here as well.  Lastly, the tail of the shaft has pre-exisiting cosmetic marks but is functional and we will use as is.  No other dimensional deviations were noted for this repair.

SOLUTION

The following actions were performed on this Brother TC-229N spindle:

• Clean, inspect overall dimensions
• Grind, chrome plate, and finish grind the front and rear bearing journals
• Replace bearings, Bellevilles, 5mm gripper balls, o-rings, and assembly screws

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.