Shaft finishes for low friction

May 07, 2004 7 Replies

For linear bearings, we use 0.125" diam x 3.0" length stainless shafting. Sliding parts are molded Delrin. The finish on the shafting is the primary determining factor for friction. We find that even 4u rms ground finish on the shafting produces highly variable results from batch to batch. For a while, we were having the shafts electropolished, which works well, but is costly. Investigations reveal that most shafting in this type application has a 'rolled' finish that squashes down the sharp features produced by grinding. Can anyone recommend a supplier for small quantities of rolled shafting (as described above) cut to length. We use about 20K pcs per yr. Our traditional suppliers don't seem to have a clue.



Paul Mathews Mukilteo, WA USA reply via NG and/or modify this reply address: paulmBANSPAM_at_rane.com


What you're looking for is a roller-burnished finish, which can be accomplished with off-the-shelf tools in very ordinary equipment. Have a look at

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for the tooling itself. Then give Cogsdill a call. Someone in their sales department can probably put you in touch with a user of their equipment who'd be happy to supply what you need.

KG __ I'm sick of spam. The 2 in my address doesn't belong there.

Paul Mathews wrote:

Have you approached a bearing manufacturer? It may be possible to use a needle roller bearing as your shaft.

John

Thanks to the poster who suggested Cogsdill.

I think the idea is that individual needles are available in bulk from needle bearing manufacturers. They're generally shorter than what you described, but the same factory that makes them might be capable of making what you need.

-Mike-

Thanks for the clarification. Have a replies from Cogsdill. They say they haven't sold much roll burnishing equipt to job shops....their customers are mfgrs doing their own finishing...they offered to sell us a tabletop roll burnisher or roll heads that work on any toolroom lathe. We are an electronics mfgr, and we try to stay away from bringing such processes in house, so the search continues. Paul

snipped-for-privacy@pioneernet.net (Paul Mathews) wrote in news: snipped-for-privacy@posting.google.com:

Have the shafts laser hardened to about 20 microns thick. The laser will greatly reduce the peaks of the surface profile, resulting in a lower Ra, plus, you get a 90-92 RC surface hardness that is 20 microns thick. The surface finish is excellent on such treated parts, provided the surface was good to begin with. We use this treatment on air guage pins and many other parts. There is a company in Ohio that does it, but I don't have a link handy.

Anthony wrote in news:Xns94EA4C311041acziparle3sp835@216.77.188.18:

Oops...didn't notice the SS, might need to talk to them and see what hardness they can get on SS.

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