Ross,

You need to preload the bearings before checking anything.

With all taper bearings, they need to be overtightened slightly, and when the machine is started after a non working period of say 1 hour or longer, it needs to be run without any cutting being done for about ten minutes.

During this time, the bearings will generate heat, and the lathe spindle will then heat extend by anything up to about 0.005". This then cancels out the preload and you end up with perfect running bearings with no end float. If you don't do this warm up period, and use the lathe straight away from cold, anything you machine, until the spindle has warmed up, will tend to have bad surface finishes and tolerances.

Then, only after this warm up period, can your check the bearings for brinelling. They should feel as smooth as silk, if not, they either need to be replaced or have the races reground.

I wouldn't charge for any work done, just you pay the postage charges. Unfortunately, I am in no fit condition to get into my shop at this time.

If you take the bearings to any bearing factor, they will recommend what is available to you.

For preloading, you should really get the friction figures for the bearing, and using a spring balance and an arm in the chuck, you check the 'pull off' pressure, that is the figure required to get the spindle to turn from a standstill position before spindle warmup, and adjust the end nut until the correct reading is obtained.
If the figures for the bearing are not available, I usually tighten up the spindle until you either start to feel friction against turning or there is no end float, then turn the nut between 1/16th to 1/12th further. This will give a general setting that will work in most cases.

Most the people who have tapered bearings don't do this preload setup, and start to complain when they get rough finishes, then they blame either the bearings or machine, rather than themselves for not setting the bearings up correctly in the first place.

If you are not going to be using the machine for say a fortnight or more, I would recommend you release the preload on the spindle, and preload again when you next come to use the machine. The bearings should then last a lifetime.

I can't work in my shop at this time, but I still go in once a week and spin the lathe up for quarter of an hour. This ensures that the bearings don't 'settle' in a fixed position and they get a bit of lubrication.


John