John Woodgate wrote:
I read in sci.electronics.design that pest3125
wrote (in . com) about
'The PEST project - completed.', on Tue, 11 Oct 2005:

It needs to be made of hardened steel for ball bearings to work well.


Try aluminium with a smear of oil. It's a little-known fact that Al/hard
steel is a non-wearing combination. See Austin 7 crankshaft main
bearings. Ball and roller races directly inserted in an Al casting(;-)

Depends on the load, hardness of the AL and lubrication.
I'd suspect that the impact would peen the AL badly.