Heald Red Head 407 Spindle Repair

The Red Head 407 is one of many models that Heald manufactured for internal grinding applications.  It can be found on many different makes and models of grinders, but is most commonly found on older Cincinnati Milacron machines.  This specific spindle runs up to 25,000 rpm and is belt driven.

CHALLENGE

This Heald Red Head 407 spindle arrived at Northland Tool and Electronics in rough condition.  The bearings were noisy and felt rough when spun by hand.  Upon disassembling the spindle, it was found that all the bearings were extremely worn and needing to be replaced.  The spanner holes in the front shaft nut were damaged and the nut would need new holes made 90° from the existing ones.  The critical dimensions (bearing journals, bearing shoulders, housing, etc.) were then measured and only two showed signs of wear and needing attention during the repair.  First the 72mm front housing bore was worn tapered and out of round.  Second the quill pilot face measured excessive runout greater than 12μm.

SOLUTION

The following actions were performed on this Heald Red Head 407 spindle:

• Clean all parts of the spindle
• Replace all bolts and o-rings
• Replace bearings
• Add new spanner holes to front shaft nut
• Grind-Plate-Grind (GPG) 72mm front housing bore
• Kiss grind the quill pilot face

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.