Kuraki KH-80 Spindle Repair

The Kuraki KH-80 is a CNC vertical machining center.  It comes equipped with a grease lubricated and belt driven spindle capable of running up to 6,000 rpm.

CHALLENGE

When this Kuraki KH-80 spindle arrived at Northland Tool and Electronics we completed a breakdown and evaluation of the spindle.  Upon inspection we noted that the bearings failed from coolant contamination(front quad set had coolant residue in them).  We always measure all critical dimensions (bearing journals, housing, taper, etc.) and found a few issues on this spindle.  First the shaft taper was bell mouthed and the gripper fingers were showing signs of wear.  Second, the drawbar shaft and bellvilles were very pitted and rusted.  Third, the rear 85mm roller journal was undersized by -4/-6(ISO is +3/+13).  Lastly, there was a tap broken off inside of a hole in the shaft tail which will be removed.

SOLUTION

The following actions were performed on this Kuraki KH-80 spindle:

• Clean, inspect overall dimensions.
• Remove broken off tap in shaft tail
• Replace bearings, drawbar shaft, grippers, bellvilles, o-rings
• Grind, plate, and finish grind (GPG) BT 50 taper and 85mm rear roller journal on shaft
• GPG drawbar 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.