Flat Linear Needle Bearing Cage for gibs

[Vogavt]

Examples:
http://www.ikont.co.jp/global_data/d.../cat6607FT.pdf small file - Go to page 6

http://www.icb-usa.com/media/kmf/Lin...ges(k35_0).pdf larger file - Look at first page

I can't find pricing on any of all the sites I've looked at. "Request Quote" only.


Anyone ever think about using a flat needle roller cage in place of the gibs?

I would think some modification to the gap between the surfaces would have to take place to accommodate the thickness of the cage (depending upon how thin of a product you could find).

I realize there would have to be some sort of shim on the gib adjustment side, but I'm not sure one could ever get a thick enough material to take the load, UNLESS the dovetail gap was widened.



Just thinking...

Vogavt

[hndswthtshdws]

Bearing races are hardened. Dovetails are not hardened.

I think if you tighten everything enough to get some rigidity out of it, you will deform the dovetails slightly and things wont roll.

[SCzEngrgGroup]

If this were a good idea, you would've seen "real" machines doing it long ago. In fact, it would almost certainly work horribly. Ball and roller bearings work because BOTH side of the bearing are able to roll on their races. This REQUIRES that the balls/rollers be able to move relative to BOTH the support and the load whenever there is motion. Using those linear bearings in mill ways, they would be able to move only as far as the end of one of the ways, then stop (or, all fall on the floor...). At that point only ONE side would be able to roll, and the other would have to slip, or they'd both alternate between slipping and rolling. In either case, friction would increase dramatically, as would wear. Try to think of a ball bearing, where you glue the ball retainer to one of the races. How well would that work?

Regards,
Ray L.

[Vogavt]

Bearing races are hardened. Dovetails are not hardened.

I think if you tighten everything enough to get some rigidity out of it, you will deform the dovetails slightly and things wont roll.

Okay, so why not put hardened material on "both" sides of the cage and "fix" one side within the shim? Say inside of a small rectangularly pocketed shim that just fits the cage within it and to where the bottom side of the pocket doesn't touch the needle bearings (otherwise they wouldn't roll).

This way the cage would stay in place and all the needle bearings wouldn't fall out.

I guess there's a reason that big machines haven't been using this method, but could it be they've never thought about it? Rhetorical question, but did either of you happen to think about this before. (no, this is not an arrogant question, just food for thought)

BTW, thanks for the quick responses!
Vogavt

[keebler303]

Ray explained pretty well why nobody does it.

Matt

[LUCKY13]

In the first link if you scroll on down the PDF they have hardened races that go along with the system if needed. They also have a recirculating shoe type much a like a block on a leiner rails system.


Personally I think this has promise. One thing with the right design the clearance could be ajusted to fit the need. The double angle rails they show should make good dovetail systems when mounted in cast iron tables/saddles, but it would need to be a recirculating type. Its the same things as a liener rail & blocks but in a different config.


That said its going to cost as much or more if hardened rails and recirculating shoes are used.


But yes just to use the bearings on cast iron will not work, they will eat the cast even if hardened.



Jess

[Vogavt]

Looks like someone's already thought about it. Sorry for the large image. Can't figure out at the moment how to make the smaller jpg thingy. LOL!

Not sure I understand the bolt at the top right pointing downward. Seems like there would have to be a lot of slop to enable the part to move horizontally.

[kawazuki]

Looks like someone's already thought about it. Sorry for the large image. Can't figure out at the moment how to make the smaller jpg thingy. LOL!

Not sure I understand the bolt at the top right pointing downward. Seems like there would have to be a lot of slop to enable the part to move horizontally.

Gotta admit its a neat solution although maybe overly complicated compared to using linear rails and blocks! It seems to score in overall height but loses with the multitude of precision bearing 'blocks' required and the possiblity of warping and misalignment! Also the load bearing is compromised in that orientation - if they were turned through 90 degrees like a traditional lathe vee bed that area would be improved 100% but you'd lose rigidity! Still, 'thinking outside the box' progresses the artform