bearings and ballscrew dont fit each other

[Gary]

The tolerance on the machined end of the ballscrew should be between -0.008 and -0.015mm.
This is a tight tolerance to achieve on a lathe and would normally be ground.
if it is too tight, i suggest using the method Jazz mentioned, or putting it on the lathe and use a fine emery cloth to take it down slightly.

Thanks for reply,

I'll try a clean up first. Your right that the calipers can be out but I do think the shaft is bigger than the bearings. I also noticed that on the shaft to motor coupling, neither hole is the right diameter for either the ballscrew or motor shaft. I'll post the measurements later and see if that helps explain the situation. Hopefully a cleanup and emery will work however :)

[Jonathan]

or putting it on the lathe and use a fine emery cloth to take it down slightly.

That's probably the best option - I have to do it all the time to ballscrews from Chai. Freezing the ballscrew and/or heating the bearings can get it to slide on to the shaft, but you risk there being too muck friction which may stop you being able to pre-load the angular contact bearings since they require a 'just sliding' fit.