Re: Ballscrew balls ?

I have just refurbished a CNC lathe. I serviced the 2 ballscrews
however on reassembly I have a .05 mm backlash in the Z axis. There
were originally a few damaged balls in it and I replaced them with new
ones. (Metric ballscrew uses imperial balls ???)

"But you CAN improve things greatly by using oversize balls and
running them in"

How oversize can you go and how do you run them in ?

Thanks Wallace

> Higher grade (ground) ballnuts use two sizes so that the balls rolling
> the "wrong" direction are not load bearing.
>
> Think about it, in the loaded state, a given ball is rolling against
> both its neighbor balls AND the housing. Causing sliding when all
> balls are the same size. Now sliding is a VERY bad thing where
> efficient motion is concerned...
>
> If every other ball is smaller, then the ones going the "wrong way" do
> not slide against the housing, only their neighbor balls. Sliding is
> reduced.
>
> But you CAN improve things greatly by using oversize balls and running
> them in, and then re-loading with fresh--oversize--balls. It's a very
> good way to maximise the effectiveness of your inexpensively purchased
>