Kitamura Bridge Center-8 Spindle Repair

The Kitamura Bridge Center-8 is just as the name says.  It is a bridge style CNC vertical machining center.  It comes fitted with an oil mist lubricated and gear driven spindle capable of running up to 10,000 rpm.

CHALLENGE

This Kitamura Bridge Center-8 spindle’s bearings were noisy and felt rough when rotated by hand in assembly incoming.  After disassembly, we noted that the front bearing quad set and rear roller all felt very rough when rotated by hand.  There was also fretting noted on all the bearing races.  We then measured the critical dimensions (bearing journals, housing, taper, etc.) and found a few issues.  First, the tooling taper ID had high runout of 4µm.  Second, the 80mm front bearing journal had very high runout >5µm.  Lastly, the drawbar was heavily contaminated and the drawbar nut was stuck on and had to be machined off.  No other significant dimensional deviations were noted.

SOLUTION

The following actions were performed on this Kitamura Bridge Center-8 spindle:

• Clean, inspect overall dimensions
• Rework damaged drawbar threads
• Grind, chrome plate, and finish grind the 80mm front journal
• Kiss grind the tooling taper ID
• Replace all bearings, drawbar nut, 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.