Changing Balls in Ballscrews?

[Model Maker]

I have Thompson ballscrews on my Mini Mill CNC conversion and have some backlash in the Y axis. I have heard of putting larger balls in the ballscrews to remove the slop, I removed the balls and mic'ed them (0.1248). Has anyone done this before? I know where to get bigger balls in packs of 100 but I have no idea of how much bigger balls to get. There are 69 balls in the nut so is a ball a couple of tenths bigger a good place to start? I don't want to get balls that aren't big enough and I don't want to get some that are too big. Is there a way to figure this out scientifically? I don't want to buy a bunch of balls that I can't use, if you know what I mean.

http://stores.ebay.com/ToolSupply/B...8&_sid=74456173&_trksid=p4634.c0.m322

Thanks for any help

Model Maker

 

[Model Maker]

The new oversize balls arrived today from Florida and they went in the ball-screws without a great deal of effort. I practiced putting the balls back in while I was waiting for the new ones to get here. The mill is now back together, and after checking I now have about 0.001 backlash in both the X and the Y axis. I suggest that "It's good enough for the girls that I go with" and I am a happy camper. I will be making some more little parts tomorrow.

I know everybody said that I will wear out the screws early but my little mill sees very little running time and they will probably outlive me. Best $27.00 that I have spent in a long time.

Model Maker

I just love it when things go right for a change.

 

[Tony Wells]

It would be interesting to develop a relationship between the backlash with the first set, and their size, compared to the new size, and the current backlash. Perhaps you could find another size ball a tad larger and do better yet.