Re-ball ball nuts

Hi. I'm trying to squeeze out as much backlash from the SFU1605 ball screws as I possibly can from my new build. I've already replaced the bearings in the support bracket with angular contact bearing.

I have the Z-Axis screw apart and have measured the balls using a micrometer. All of them measure between 0.12530" and 0.12535".... So gonna call the average 0.12532".

I was thinking about 5 ten thousandths (.0005") seemed reasonable. That would put the new baseline @ 0.12582". Of course actual size will depend on what is commercially available.

Is there a rule of thumb or some general guideline on how much oversize one should go.. at least as a starting point?

Here are a couple of pics of the machine I'm working on.

I'll make a few comments, maybe helpful, maybe not. Does your application have room to double nut your ball screw? This gives you the ability to "dial" out any backlash. My second thought would be to email Dave Clements who is very intimate with ball screws and re-balling them. He's a busy guy, so I'm not sure how timely his response might be, but it's worth a shot! This is the site. https://www.arizonacnckits.com/index.html

This is his info contact email address. '[email protected]'

Stuart

Double nuts would require redesign/re-modification to parts for all three axes... but YES this could be an option. My Y-Axis ball screw is a Left-Handed screw... so finding just a double-nut would be challenging. Guess I could go back to the folks I purchased the LH screw from and see if the have a double-nut option. For now I went ahead and ordered balls that are 0.1258"... we'll see what that does.

The amount of play you have is not the same as how much you need to increase the ball size. You are fitting the balls in a V but really its more like exponential curve. Some times a small change in ball size can make a lot more difference than you think. Getting cheep balls is a PIA too so if you do Balltek it cost way too much to play around with the sizes. When you measure a normal mic will report the ball as smaller because of the small contact area. You need to set zero with a ball of known size. I think the .0005" is a fair guess but I don't know how loose they are.

If your not in a hurry I can re pack them for $35 per screw. I have a few thousand balls laying around.
Email me at [email protected]