Fortuna FIV60R250.44 Spindle Repair

The Fortuna FIV60R250.44 is an ID grinding spindle.  The spindle we repaired here is grease lubricated, belt driven, and is capable of running up to 24,000 rpm.

CHALLENGE

This Fortuna FIV60R250.44 spindle was sent to us with our customer indicating that the spindle was heating up and was hard to turn during operation.  Upon disassembling the spindle, we noted that the front press-fit shaft nut was backed off incoming and the ID was worn oversized/egged -3/+20µ.  The pulley retention nut was also loose and the bearing pre-load spring pack was stuck.
We inspected the bearings closely and found that the front bearing pair was contaminated and most of the grease was washed out.  Critical dimensions (bearing journals, taper, housing, etc.) were then measured and we found a few issues.  First, we found that the tooling taper ID had 10µ runout and the face had 12µ runout.  Second, the pulley taper OD measured 8µ runout.  Lastly, the 47mm front housing bore was scored and egged 0/+8µ (ISO is ±5.5µ).

SOLUTION

The following actions were performed on this Fortuna FIV60R250.44 spindle:

• Clean, inspect overall dimensions
• Replace bearings, o-rings, and assembly screws
• Manufacture and install new front press-fit shaft nut
• Grind, chrome plate, and finish grind the 47mm front housing bore
• Kiss grind the tooling taper ID, face, and pulley taper OD

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.