Thread: Lathe spindle bearing

Originally Posted by rfurzer

I want to remove the left hand bearing on my AL960- to get to the sliding gear. The parts list shows a bearing cap then a nut ( locked by capscrews closing a slit).
Is it a matter of removing the bearing cap, marking the position of the nut, taking it off and the bearing slides off?
Is resetting the preload a matter of putting the nut back where it was ( like a Salisbury diff)?

I am not familiar with your particular machine. You may get better advice from another AL960 owner... But based on experience with similar lathes, and assuming yours has two tapered roller bearings, I have some hints that may help....

- first take the preload nut off. to do so, you may first have to take out a grub screw that fixes the nut to the spindle. Watch out, sometimes there is a brass plug under the grub screw to protect the spindle thread. Sometimes there may be two short grub screws in tandem.
- now you should be able to drive the spindle out towards the tailstock. With very well made lathes that can be done with a copper hammer. But in my experience the inner races of Chinese lathes are an extremely tight press fit onto the spindle. You may have to make a spindle puller to gently get the spindle out. Do not take the mallet.
- when re-installing you may first have to do something about the overly tight bearing fit, unless you were lucky and your machine is not overly tight.
- the bearing preload on a lathe is very considerably higher than on a car wheel. There are several methods to do this. Lacking proper factory setting instructions, the safest is to adjust preload based on headstock temperature rise. Too high a preload will overheat the bearings and quickly destroy them. Insufficient preload means poor surface finishes and problems to keep accuracy.

Thanks