Okuma HF-802 Spindle Repair

The Okuma HF-802 is a CNC grinder.  It comes fitted with this oil mist lubricated and stator driven spindle that is capable of running up to 60,000 rpm.

CHALLENGE

This Okuma HF-802 spindle was partially disassembled incoming.  The customer provided a replacement shaft and a quill.  The customer also stated that the original OEM shaft in the spindle was cracked. We confirmed that it was unusable.

The replacement shaft had several dimensional discrepancies from the original:
– The new shaft was 3mm longer overall, the extra length was in the quill pilot area.
– The front and rear journal shoulders were 100µm further from each other. (previous measurement was incorrect)
– The threads of the 6mm quill pilot ID extend into the pilot surface, we cannot measure pilot runout.
– Quill runout after assembly into the pilot was >100µm.

SOLUTION

The following actions were performed on this Okuma HF-802 spindle:

• Clean, inspect overall dimensions
• Grind, chrome plate, and finish grind the 6mm quill pilot ID to insure good runout
• Kiss grind the front and rear journal shoulders to match the original OEM dimension and insure proper preload
• Replace bearings, o-rings, and assembly screws
• Component balance the new replacement shaft on the Schenck balancing system

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.