[margni74]

i bought a ball screw from ebay a while back. I'm trying to locate some bearings for the motor driven-side bearing block and free end block. I'm finding some SKF angulare contact bearing on ebay, however the inside diameter is too large, and the SKF site doesn't even list bearings this small...

Heres a drawing of the screw end...


I basically need a couple of 8mm ID (THAT DIA 7.00mm from the picture is really 8mm) bearings no more than say 6-8mm wide so they can fit on the 17.5mm sleeve in the above pic.

Any recommendations where to look?

[Glacern]

Skate bearings are 8mm ID, 22mm OD, 7mm width. 608ZZ for shielded, 608-2RS for sealed.

Not A/C, but they can take a small axial load. Try mounting a pair of them and see how it works. It might be just fine for a small machine. Worst case, you replace them periodically since they cost you just 50 cents each.

[HuFlungDung]

I don't see much in that size in my bearing catalogues either. However, all is not lost.

You can easily make up a sleeve to fit the shaft, which will have a large enough OD to fit some readily available size. Hopefully, you have enough space around that screw to accomodate the larger OD of the larger bearings.

The typical fashion of retaining the bearings on the shaft with a threaded nut mean that you would be having to cut threads on this already tiny shaft, making it even more flimsy.

If you fabricate a collared sleeve, you can have a shoulder on one end of the sleeve to provide a thrust surface for one side of the bearing pack. Add enough length to the sleeve so that you can thread the other end to capture and preload the bearing pack.

Realistically, you might have to go with a 12mm ID bearing to do this.....10mm might be not quite enough to work with for the threaded sleeve.

Loctite the sleeve onto your ballscrew for a permanent fit, or fabricate a light interference fit, perhaps .0005 interference. Heat the sleeve very hot (like 600°) and assemble quickly. This is tricky to do, so Loctite is the easier method and reversible too. Loctite can be melted at about 400°F.

[margni74]

I don't see much in that size in my bearing catalogues either. However, all is not lost.

You can easily make up a sleeve to fit the shaft, which will have a large enough OD to fit some readily available size. Hopefully, you have enough space around that screw to accomodate the larger OD of the larger bearings.

The typical fashion of retaining the bearings on the shaft with a threaded nut mean that you would be having to cut threads on this already tiny shaft, making it even more flimsy.

If you fabricate a collared sleeve, you can have a shoulder on one end of the sleeve to provide a thrust surface for one side of the bearing pack. Add enough length to the sleeve so that you can thread the other end to capture and preload the bearing pack.

Realistically, you might have to go with a 12mm ID bearing to do this.....10mm might be not quite enough to work with for the threaded sleeve.

Loctite the sleeve onto your ballscrew for a permanent fit, or fabricate a light interference fit, perhaps .0005 interference. Heat the sleeve very hot (like 600°) and assemble quickly. This is tricky to do, so Loctite is the easier method and reversible too. Loctite can be melted at about 400°F.

i like the sleeve idea. I just need to figure out how to fabricate a sleeve. ANy suggestions? you mentioned end thread, and it made me realize there was some actual thread on the end. I took a pic and marked the dimensions...so much for my detailed cad drawing.



I think you're right on 12mm ID, they seem to be abundant from several different vendors. After a bit more searching a company called alpine bearing had AC bearing in the 6mm and 7mm ID's, i may call them start of the week, although im not sure they are going to be able to supply me with a measly quantity of 2...

[lgalla]

https://www.misumiusa.com/PDFViewer....=true&Page=325