HSD ES988A Spindle Repair

The HSD ES988A spindle is grease lubricated, stator driven, and capable of operating up to 24,000 rpm.

CHALLENGE

This HSD ES988A spindle bearings were noisy when rotated by hand in assembly incoming and rust built up on the shaft nose was preventing ejection of the tool.  Upon disassembling and evaluating the spindle, we noted that the rear bearings were full of particulate and the OD of the outer races was fretted.  The motor also contained excessive particulate buildup.  We then measured the critical dimensions (bearing journals, housing, taper, etc.) and found a few issues.  First, the HSK face had high runout of >5µm and the taper had 2µm runout.  Second, the 45mm front bearing journal was undersized -20µm (ISO = ±3.5µm).  Lastly, the front shoulder had high runout.  No other dimensional deviations were noted for this repair.

SOLUTION

The following actions were performed on this HSD ES988A spindle:

• Clean, inspect overall dimensions.
• Grind, chrome plate, and finish grind the 45mm front bearing journal
• Kiss grind the front journal shoulder
• Kiss grind the HSK face and taper to address the high runout
• Replace all ceramic bearings, 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.