Bearing race nomenclature

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BadDog
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Bearing race nomenclature

Post by BadDog »

I find myself in need of new bearing races for rebuilding an art-deco 50's shop floor jack (Blackhawk S-4), and can't seem to find any options. And I suspect it's because I don't know the right nomenclature. I'm hoping someone here can help.

The caster wheels have a 1.125" (actually measures undersize close to 1.1") stem that mounts and locates the caster axially without a dedicated bearing. The thrust bearings are the ones in question, and they provide some level of centering in their design. It uses loose 1/4" ball bearings, of which I have a supply. It looks a bit like a bike stem bearing without the cage.

But the top races are broken/destroyed, and one of the bottom races has lost much of it's bearing surface. The best of the race, and the only one reasonably intact, is linked below. As you can see, it's rather sad too.

So, can anyone tell me what terms to use to find such an animal?

Click to see remaining race
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whateg0
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Re: Bearing race nomenclature

Post by whateg0 »

There's a S4 thread on GJ. Might ask there too. Mine is buried in the garage behind an engine but I need to get the engine out and work on it this weekend. I'll try to have a look at mine. They might have been custom made just for this Jack but I don't know. I don't think they are really a thrust bearing but more of an angular contact bearing, btw.
Russ Hanscom
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Re: Bearing race nomenclature

Post by Russ Hanscom »

Nothing too fancy - make your own out of stock and harden a bit if you only need a few?
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BadDog
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Re: Bearing race nomenclature

Post by BadDog »

Thanks.

I've seen a few S-4 threads on SJ, and participated on one or two. There was a guy on one thread who "had a machinist friend make one" for him. But I need 4, and would have to acquire suitable material to make them, and harden them, with concern about finish scale with no practical way to grind. I suppose that I could buy some pre-hard material, which would likely be good enough for my needs. If it was a major important project I might take it as a challenge, but for a floor jack I just want to make usable, I would much rather just buy the races if I can.

And if such a thing turns out to be proprietary, no longer available, or some other form of unobtanium, it think it might be easier to modify this to take a fork stem bearing, angular contact, or even a taper bearing before trying to make the races without being setup for it.
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Harold_V
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Re: Bearing race nomenclature

Post by Harold_V »

Explore commercial thrust bearings imported from China. Not suggesting that's a solution, but it could be. Dunno. Not familiar with the jack in question. They may not fit.

If push gets to shove and you must make new races, you should achieve acceptable results making them from 17-4 PH stainless. It's easy to heat treat and should get hard enough (40+ Rc) to provide years of service for a guy who isn't using the jack daily.

17-4 PH heat treated to condition H-900 will proved scale free parts, so they can be finish machined before heat treatment and require no other attention, although you would have the option of spin polishing (for finish) after heat treatment if you so desired. It is known to shrink a few tenths per inch upon heat treatment, but that is likely of no consequence for your particular application.

H
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liveaboard
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Re: Bearing race nomenclature

Post by liveaboard »

Or clean up the old races and add new balls.
I watched my Indian machinist recut that sort of race on his lathe with carbide. Obviously, getting a precise radius isn't easy, but it doesn't have to be super accurate since it's only a castor and hardy moves.
If there are no ridges, emery will clean off the corrosion.
New balls are easily available.

Older motorbikes had races and loose balls like that in the steering stem, bicycles wheels too.
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BadDog
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Re: Bearing race nomenclature

Post by BadDog »

Harold:
Thanks, fantastic information. That appears to eliminate most of my reluctance for machining. Since I would have to use HSS to provide the form tool producing the rather large bearing surface at one shot, I imagine that 17-4 PH could be a problem with chatter and work hardening. I can envision the form tool geometry along the line of a fat-round trepanning tool fed from the tailstock (due to OD ball retainer lip). Can you provide advice for success? Definitely not something I've ever tried before.

Also, the single bearing assembly provides primarily thrust management, but also acts like an angular contact (as whatego mentioned) to control off-axis movement as well. So a simple flat race for a typical thrust bearing wont' work here.

Liveaboard:
If I had 4 races like pictured, that would absolutely be my path. But the 2 uppers were completely missing, and I can only imagine the broke and fell out years ago. The other lower race is missing sizeable chunks from the horizontal bearing surface, and had lost all of it's balls. The lower race pictured was the only one still whole, and in spite of loosing it's upper race, the balls were still there due the enclosing upper socket.

I'm still hoping to find something ready made, but having been reviewed by several here with much more knowledge than I posses without any likely pointers, I'm increasingly pessimistic about a positive outcome. Whether I make my own races, or consider retrofit to an available bearing of some sort, I need to make an accurate survey of dimensions to see what I have to work with. The closest thing I can find among readily available bearings are fork stem bearings like attached here. Perhaps that will do, though I'm not sure how well it will hold up to lift various portions of 6-10k lbs verhicles. The absolute limit would be something less than 1/2 the total vehicle weight, with almost all the weight on the jack load wheels, I suspect that if I can match dimensions, it should work for my purposes.
stembearing.jpg
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Harold_V
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Re: Bearing race nomenclature

Post by Harold_V »

BadDog wrote: Thu Apr 15, 2021 1:07 pm Since I would have to use HSS to provide the form tool producing the rather large bearing surface at one shot, I imagine that 17-4 PH could be a problem with chatter and work hardening.
If you are not familiar with 17-4, it's an interesting experience. It machines beautifully, although it is not free machining. Easy to get good surface finishes, though, and that's important for your particular application.
I can envision the form tool geometry along the line of a fat-round trepanning tool fed from the tailstock (due to OD ball retainer lip). Can you provide advice for success? Definitely not something I've ever tried before.
A form tool for tailstock use would most likely be beyond your capability. Without a cutter grinder with radius capability you'd struggle to get a cutter that made contact on all teeth.

Given this project was mine, and I chose to make the new races, I'd do it with a single cutting edge, mounted in the conventional tool holder on the carriage, what ever it may be. With your large lathe, you should be able to make a plunge cut at slow speed and achieve the desired results. Needless to say, the larger the machine, the better the results that would be achieved. Chatter can be a problem, of that there is no doubt.

If your tool has desirable rake and clearance, so long as you keep it cutting there should be no work hardening. Because 17-4, for the most part, does not tear, surface finish would be quite acceptable. That's assuming you keep the cut well lubricated, which, in turn, will limit chip welding, the chief cause of a torn cut with this material. When conditions are correct, the resulting cut is mirror-like.

Keep the form tool extension short, use an indicator (or a DRO) to witness travel, and have at it. Light depth of cut is the order of the day. 17-4 does not horse well, and responds quite nicely to positive rake. Balance rake with end clearance, to avoid hogging (self feeding).

The PH in the designation means that the material is precipitation hardening. It does not rely on the carbon cycle to achieve hardness, but on grain growth instead. The material, as a result, is quite stable, aside from the already mentioned shrinkage.

You can do it. It will require your attention.

H
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BadDog
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Re: Bearing race nomenclature

Post by BadDog »

Sorry, I meant fed in axially toward the chuck, not literally from the tailstock. Bad choice of words on my part. It was more about the clearance dealing with that axial feed direction where almost none is required on the inside, but extra required on the outside, somewhat like the difference in clearance required for an OD threading tool vs ID threading. That would leave the outer lip proud to aid in locating/retaining the loose ball bearings.

From what you describe, it seems well within my means, as long as I start with enough stock to allow for a few learning (aka failed) parts. Rake on a 1/4" semi-circular form tool will be "fun", but I've done similar before with a carbide ball die grinder burr. Likely roughed close with a couple of calculated stepped square cuts, then just finished to size with the form tool, then part off. That would leave full engagement of the form tool to the last 0.030 or so feed after the steps are gone

Thanks for all the information. I've got a local bearing house looking for something dimensionally similar and economical enough to put into a floor jack. Something close enough I can machine the jack parts, or make a sleeve, or whatever. The one angular contact I found sit close dimensions on MMC was something like $300.

It's looking increasingly like I need to start sourcing some 2"(+) 17-4 PH and just get on with it. Phoenix is a big town, maybe I can find it locally.

Side note: I thought PH was Pre-Hard. :oops:
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BadDog
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Re: Bearing race nomenclature

Post by BadDog »

I found this at MMC.

Presumably what I need is the hardened version of this? Oddly enough, it's cheaper than unhardened. Obviously I would be better off with the hardened variety, but I wanted to make sure I don't buy $66 (+shipping) material that won't respond to HSS. Is it safe to assume your description applies to this hardened material? Given your description about heat treating after machining, I'm guessing not...
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Harold_V
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Re: Bearing race nomenclature

Post by Harold_V »

No. Not a hardened version. It should be condition A, so you can harden the parts after machining. The condition of the offered material is probably H-1150, so it's much softer than the H-900 condition that would provide the greatest wear and brinelling resistance condition. If you make that material your choice, I am assuming you won't have the option of further hardening, as it has already been heated beyond the H-900 condition. In such a case, like aluminum, in order for heat treat to be altered, the material must be returned to the solution annealed condition.

This material has some strange machining characteristics. When you figure out how it cuts, it's actually not bad to machine. Obviously, it would machine much nicer in the softer condition (A). You'd struggle trying to machine the H-900 condition, but it can be machined.

There's a substantial difference in hardness between H-900 (about 45 Rc) and H-1150 (about 30 Rc).

H
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BadDog
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Re: Bearing race nomenclature

Post by BadDog »

Thanks for taking the time to cover all that. I've only got a few feelers still out there, and hoping one pans out, but it's looking increasingly likely I'll be needing to follow your advice.
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