The rear shaft threads on this spindle were worn and were cut into the pulley mounting surface. This caused irregular run out on the pulley resulting in vibration. We fixed the pulley mounting surface and cut new threads in our machining and grinding departments. We then assembled the spindle in our clean room, test ran and put it through our final quality check. The spindle is as good as new which is a good thing as no replacement spindles were available for the machine.