Seattle .125 ball bearings ( needed for ball screw repair / rebuild )

C

cut2cut

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I'm in the Seattle area and hoping there is another hobbyist in the area that has extra .125 ball bearings. To be precise, I'd prefer ones just a bit smaller as I'm trying to diagnose why my ball screw is tight. Outside of that, I suppose it is possible that one ball was missing from the factory but I'm not experienced enough to know if just a ball or two missing could create so much friction. I've torn it apart, cleaned and regreased it but the issue remains after reassembly although slightly smoother.
Any advice, and or if anyone in the Seattle area is hoarding an abundant supply of =< .125 ball bearings, I'd appreciate the help. I'm trying to avoid losing the use of my mill for 2 weeks if I have to send the ball screw away to be fixed or worse replaced.

Jake
 
3mm balls are very close to, but slightly smaller than .125" balls, 3mm is .1181". Measure the balls carefully.
 
A bicycle repair shop may have what you want. When I needed a ball for detent, the guy just handed me 3 of them.

Craig
 
Balls for use in ball screws come in standard size as well as varied degrees of oversize. A slight difference in size is very noticeable in the assembly. The oversize balls are often used when ball screws are repaired or reconditioned. Just a heads up on this.
 
Diecutter said:
Balls for use in ball screws come in standard size as well as varied degrees of oversize. A slight difference in size is very noticeable in the assembly. The oversize balls are often used when ball screws are repaired or reconditioned. Just a heads up on this.
Click to expand...

Thanks to everyone that has posted. Much appreciated! I measured every ball and it seems all are 0.1250 to .01251 besides one that is well undersized at 0.1244. Its difficult to quantify and relate to anyone how tight it is but I've seen videos and previously repacked ball screws on my old mill and usually the ball screw could turn almost on its own weight if vertical. This ball screw is far from that as you can see in the attached video.
Basically, I'm trying to determine which undersized balls to buy, so looking for opinions ( best guesses ). At $12 a set I don't want to have to buy 5 sets and be way off the mark I'm leaning toward buying .1240 and 0.1246 but maybe I should go even smaller. Any thoughts are appreciated.

Jake

 
In general I would prefer a nut that is on the tight side. It is hard to tell from the video, but it looks like it turns smoothly with some preload. Preload means zero backlash and that is the end goal. I would not want to be able to spin the ball screw with my fingers. Keep in mind there is also some small friction from the end seals.

I would anchor the nut to something and run the ball screw through it a number of times with a drill to loosen things up a bit. One trick you can do is to use two different size balls. Then alternate one large and one small as you pack it, this reduces the contact area by half and thus reduces the friction.
 
JimDawson said:
In general I would prefer a nut that is on the tight side. It is hard to tell from the video, but it looks like it turns smoothly with some preload. Preload means zero backlash and that is the end goal. I would not want to be able to spin the ball screw with my fingers. Keep in mind there is also some small friction from the end seals.

I would anchor the nut to something and run the ball screw through it a number of times with a drill to loosen things up a bit. One trick you can do is to use two different size balls. Then alternate one large and one small as you pack it, this reduces the contact area by half and thus reduces the friction.
Click to expand...

Cool, thanks for the advice.
I ordered some cheap ball bearings from Amazon that arrived this morning! I was hopeful, by luck, there were enough under .125 that I could test the size with. Well, of the 120, there were JUST enough under .125 that I was somewhat confident I'd be able to see a difference. Yup, its a marked difference yet still has some drag. I'd say its still tighter than I'd think was perfect, but it has some preload. So I feel pretty confident I can get some quality high tolerance balls in the 0.1247 range and i'd be set. I still feel an odd "crunchiness" on occasion which baffles me but considering the variety of sizes in the "cheap" Amazon ball bearings, its understandable, or perhaps I could have added one more ball in than I did. Perhaps the screw itself has been harmed by oversized balls.... Tough to say yet. If I come to any conclusions, I'll be sure to share them.

p.s. the seals were loose earlier in the video and in testing I was leaving them off too. They do cause a bit of drag but not too much.

Thanks again,

Jake
 
McMaster Carr carries a assortment of balls metric and standard. Quality too and very reasonable.
 
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