[Mihkel615]

Hello. I have a bit of backlash on my ballscrew (0.002")and I'm thinking of just reballing it. I know I should have it regrind too but I cant afford it right now. I was thinking reballing with bigger balls. I measured my current balls and they were 0.001" smaller then 1/8" witch is I think the original value. If I change them with original value I will get rid of half of backlash, but how much bigger balls do you think I can put in without the risk of jamming? There is a little groove in the bottom of the screw thread and but else then that, the screw should only have wear to the sides and if you think about the geometry then the bigger radius ball can easily jam. Thats why I'm thinking just a little bit bigger ball and maybe when it runs for while I can reball again for bit bigger again. What you think?

[underthetire]

Is it a split ballnut?

[Mihkel615]

Unfortunately it a single nut. Ground NSK with two ballreturns to be exact.

[underthetire]

Double check, sometimes they load a large ball, smaller ball, large ball etc. I've re loaded screws with larger bearings in a pinch, but they were a split nut, so adjusting preload was easy. Where you run in to problems is at the ends where the screw doesn't wear as much.

[Mihkel615]

Yes, the balls were loaded bigger-smaller-bigger-smaller. I'm used to millimeters, so without converting, the bigger balls measured 3.14mm and smaller 3.09mm. 1/8 inches is 3.175mm. I think I'll order 3.18mm balls and 3.20mm balls. If it works with 3.20 then I'll have a (almost) zero backlash screw, but incase they wont fit in I'll load it with 3.18mm ones.

The worry is at the moment- Will the screw jam badly or some other horrible scenario occur with 3.20mm ones?

[Mihkel615]

Ok, I educated myself a little bit and should be embaressed for not doing it before. The groove in the screw is not matchy-matchy with ball at all, more like a contact point at 45 degrees. This changes the picture in my head and I dont think it will jam. The problem now is that the only way to preload it is to have a few microns bigger balls than perfect fit.
I guess I'll have to forget about preloading when I do it myself.

Now, my backlash is 0.07mm, measured my bigger balls 3.14mm. In this light I think I'll go with 3.21mm balls, order 3.20mm balls for backup and see what happens.



this is the picture that showed me light to the subject
and heres the talk
http://machinedesign.com/article/bal...the-myths-0708