Mori SL1 Ballscrew backlash and should I go with bigger balls?

So I'm retrofitting a Mori SL1 Lathe and there is .005" backlash in the Z axis. Too much to use compensation, I think. So far I've received quote from $1300-$1800 to recondition it. I've found new NSK 36mm Ballscrew and Nut with 10mm lead Grade C5 for $425.

So I'm wondering should I not bother with a new screw and have the old one reconditioned or should I try bigger balls in the old screw?

If I were to go with bigger balls how would i go about that? I mean what size should I go up from the original?

Ok so no joy here?

So I went with bigger balls. My originals were .2805" and I replaced them with .280734" and I reduced the backlash to just under .002". I went ahead and ordered .280914" per my conversation with Eugene at Baltec.

Now I'm wondering if the double ball nuts need to be loaded, ether toward each other or away, to make up the difference thereby creating a anti-backlash nut. I've done this many times before on other machines I've built, but just now started to entertain the idea that these nuts work the same way.

I'm not sure if that's the case with these nuts. If they are then I'm not sure how that is achieved.

When I took them out of the lathe the spacers in between were loose so maybe the loading of the nuts from each other got loose.

From the pics you can see the spacers and two metal bars on either side of the nut. They just pop in there and are held on one side with a single screw. The hole in the other end of the bar is just threaded; I assume to use a screw to get the bar out of it's slot. It's not threaded into the nut itself.

I have an idea of how i can make it work, but not as is. So I'm asking anyone here if they have any idea of these nuts are supposed to work.

I guess at this point I'm just talking to myself. Oh well.

So I totally missed it. I was thinking of the ball nut NOT on a screw, but once the nuts are on the screw, you press the spacer in between them the use the bars to secure the nuts from rotating away from each other. Those bars don't pull out cause the only way for that to happen would be one nut being loose.

Quote:

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Originally Posted by Cartierusm

I guess at this point I'm just talking to myself. Oh well.

So I totally missed it. I was thinking of the ball nut NOT on a screw, but once the nuts are on the screw, you press the spacer in between them the use the bars to secure the nuts from rotating away from each other. Those bars don't pull out cause the only way for that to happen would be one nut being loose.

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This is correct, but ive also seen the beams wear and allow rocking of the 2 nuts independently, makes for interesting ball bar results. The factory shim is typically ground so the nuts preaload towards each other, a little tip is to make a new one or shim the factory one to push away from each half. This way, you are using more of a new section of the screw pitch.

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How can the nuts preload toward each other wouldn't there need to be something to secure both nuts to each other. My side bars only secure on one end.