Makino FNC80 Spindle Repair

This spindle had a damaged taper that was causing run out in the tool. As you can see in the pictures below the taper has worn on the outer edge. This can be caused by low drawbar force allowing the tool to loose full contact with the taper and only contact the leading edge. This causes premature wear to the taper. It also causes tooling wear so please check your tools for wear before using the newly repaired spindle with worn tooling.

Possible cause of failure:
Customer indicated that spindle had bad TIR, tool rock & poor finish.
Coolant had completely washed the grease out of front bearing quad set.
Incoming shaft taper run out was 6-8µ in assembly, taper is bell mouthed.
Customer did not supply drawbar assembly, drive dogs, drive pulley, pulley keys, or pulley nut.

Recommended action:
Clean, inspect overall dimensions.
Replace bearings.
Kiss grind CT 40 shaft taper.
Adjust preload, balance, assemble and break in. Final quality control inspection.


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Repair History - Here are examples of similar spindle repairs that may contain additional information that will help you. If you have additional questions, please contact us.