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Old 08-07-08, 06:52 AM   #1
JAk
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Lapping bearing in hub?

Any one use a lapping paste on old hubs and bearings by running them for awhile, then clean and repack?
Thanks,
JAK
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Old 08-07-08, 07:13 AM   #2
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It went out of style in the 1970s with the new and improved bearings/sealed bearings that became available. Roger
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Old 08-07-08, 11:33 AM   #3
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I've heard of it. Never tried. Generally, I just repack whether it's crunchy or not. Replace bearings and ride til it's dead.
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Old 08-07-08, 01:43 PM   #4
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Never thought about that.

Usually I just put in new bearings but sometimes the races can be slightly pitted and I still want to use the hub. I might give it a try in this case...works for my valves.
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Old 08-07-08, 05:03 PM   #5
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If the races are pitted, the hard surface has spalled off. Lapping won't help. If you could lap long and hard enough to get them smooth, the hard face would be gone and the balls would be running on the soft steel base layer.
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Old 08-07-08, 05:44 PM   #6
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I'm going to try it on the old hubs with new bearings as soon as my new set arrives. Thanks for all the input, JAK
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Old 08-07-08, 06:24 PM   #7
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DO NOT USE LAPPING COMPOUND ON BALL BEARINGS! ! ! ! ! ! !

Lapping is quite a topic on it's own but it is NOT something that you do to any bearing that uses rolling elements be they rollers or balls.

Aside from the damage done to the balls themselves you need to understand how lapping works. The process relies on sliding friction and to do it right one metal (the lap) has to be a softer metal than the item being lapped. A ball bearing has niether of these charactaristics and in any case would not achieve any sort of increase in trueness or proper shaping from sticking the abrasive goop into the race.

If it was done at one time it was done in ignorance of both how ball bearings operate and the lapping process in general and no gains would have come from it other than in the minds of the perpetrators.
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Old 08-07-08, 06:26 PM   #8
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Modern high-quality bearings are made to amazing tolerances; hard to imagine you could improve them in this manner.
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Old 08-08-08, 08:18 AM   #9
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Modern high-quality bearings are made to amazing tolerances; hard to imagine you could improve them in this manner.
OP specified "old hubs". Probably there is a noticeable defect in the bearings that he's hoping to correct.
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Old 08-08-08, 08:47 AM   #10
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There well could be an issue with it but putting lapping compound in to a ball bearing is like using floor sweepings mixed with grease and expecting good results. Lapping compounds are an abrasive after all. Like any tool or material if it's used where the charactaristics will help it's a good thing. But putting abrasives into a ball bearing is not going to help restore any shaping at all. It'll just work the damage into the bearing further.
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Old 08-08-08, 11:30 AM   #11
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I'm pretty sure the OP is not expecting to use the same bearings again. I don't think anyone would expect them to withstand the process - they're disposable.
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Old 08-08-08, 11:47 AM   #12
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If the races are pitted, the hard surface has spalled off. Lapping won't help. If you could lap long and hard enough to get them smooth, the hard face would be gone and the balls would be running on the soft steel base layer.
This is true for some cones, specifically the case hardened type. But I thought the better quality ones were "hard throughout" chrome alloy of some variety. If this was the case then the cones could be refinished, not sure about the cups but I suspect the same thing.

I have had to grind & refinish bearing races on vintage motorcycles and bikes (usually Whitworth threaded) when the parts are no longer available and although I am sure this is regarded as quite the kludge the results have actually been good. I should point out that this didn't involve lapping compound but rather a small lathe and some different abrasives.

Lets just say if you can buy new ones then it is obviously the better way to go.
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Old 08-08-08, 01:39 PM   #13
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lapped hubs and new bearings

I was intending to use new bearings and after lapping discard them and end up with fresh bearings and the race and journal lapped. remember this is a vintage bike with vintage hubs. I can build a new bike on this great frame and I still want to have the vintage choice.

thanks again for all the good input,
JAK
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Old 08-08-08, 07:42 PM   #14
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If the cups are pitted then I guess you've got nothing to loose. If they are pitted badly I'd suggest looking for someone that could grind them back to true and nice. This is a touchy job and will cost big time but if the hubs are rare it may be worth it.

Cones can be chucked and new ones found. Only the most insane vintage biker will chastise you for the newer cones if they can tell the difference.

If you're going to do the bearing ball and lapping compound I would suggest you go out and find some metric or next size up from the usual size balls we normally use. That way HOPEFULLY the lapping will carve out a smooth track that is actually larger than the proper ball size so that you still maintain a single point of conact. Using the correct size will end up with the balls decreasing in diameter a little as they cut away at the bearing track and the new final balls will end up runing on two points or an indistinct wide patch. That'll add drag to the bearing. 7/32 or 5mm for doing the front and 7 mm or 9/32 for doing the rear hub.

I can't believe I'm agreeing with this but if you're desparate to save the hub then using the larger size balls will help with the outcome. Just don't use TOO large a ball. You want the lapping balls to be only slightly larger than the final size so the "track" isn't shifted out of line.

Another option would be a brass lap made to an accurate profile that includes a radius that runs in the ball track that is slightly oversize. Then you turn that inside the cup with some fine lapping compound to remove the pits. Then clean the cups and lap and shift to a finer abrasive in steps until you are finishing it with some jeweller's rouge or similar for a near mirror shine. But that's a lot more work of course. But it would guarantee better results.
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Old 08-09-08, 01:28 AM   #15
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Originally Posted by BCRider View Post
DO NOT USE LAPPING COMPOUND ON BALL BEARINGS! ! ! ! ! ! !

Lapping is quite a topic on it's own but it is NOT something that you do to any bearing that uses rolling elements be they rollers or balls.

Aside from the damage done to the balls themselves you need to understand how lapping works. The process relies on sliding friction and to do it right one metal (the lap) has to be a softer metal than the item being lapped. A ball bearing has niether of these charactaristics and in any case would not achieve any sort of increase in trueness or proper shaping from sticking the abrasive goop into the race.

If it was done at one time it was done in ignorance of both how ball bearings operate and the lapping process in general and no gains would have come from it other than in the minds of the perpetrators.
I recall instructions to lap with the old bearing balls, then clean/regrease with new balls. Your rolling v. sliding comment seems sensible, tho!
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Old 08-09-08, 01:30 AM   #16
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Originally Posted by sfclearwater View Post
This is true for some cones, specifically the case hardened type. But I thought the better quality ones were "hard throughout" chrome alloy of some variety. If this was the case then the cones could be refinished, not sure about the cups but I suspect the same thing.

I have had to grind & refinish bearing races on vintage motorcycles and bikes (usually Whitworth threaded) when the parts are no longer available and although I am sure this is regarded as quite the kludge the results have actually been good. I should point out that this didn't involve lapping compound but rather a small lathe and some different abrasives.

Lets just say if you can buy new ones then it is obviously the better way to go.
Ever done this on headset cones and cups?

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Old 08-09-08, 10:11 AM   #17
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Ever done this on headset cones and cups?

Road Fan
Yeah, it worked out ok on headsets too. The trick is to put together a way to mount the piece in the lathe, then (wearing eye protection) use increasing number (320-->400-->800-->1000 maybe) paper and wet sand the race area. Try to maintain the original profile as much as possible.

It seemed to work to remove the pits/"brinelling" and has held up to riding so far. Having said that it was a pain and I only did it because I couldn't find a good replacement, and I like to try silly things like this.
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Old 08-09-08, 11:01 AM   #18
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Yeah, it worked out ok on headsets too. The trick is to put together a way to mount the piece in the lathe, then (wearing eye protection) use increasing number (320-->400-->800-->1000 maybe) paper and wet sand the race area. Try to maintain the original profile as much as possible.

It seemed to work to remove the pits/"brinelling" and has held up to riding so far. Having said that it was a pain and I only did it because I couldn't find a good replacement, and I like to try silly things like this.
I was desparate and "restored" one cup of a headset and a couple of axle cones this way. But I used a holder for my Dremel and a fine ball shaped grinding bit to do the initial shaping to remove the pitting (thus making my own cheapie tool post grinder).

If there's pitting it will be difficult or impossible to maintain the right shape using only sandpaper unless you can use a handy round end of something that's a close match to act as a backing block for the sandpaper. Using a backing block will ensure that the paper pushes on the high spots while skipping over the low spots and will greatly help to produce better results. And it is far, far better than using it by hand even if it's folded tightly to stiffen it up. Once the first couple of grades have done their job of removing larger amounts of metal then the final polishing steps with the finer grades can be used with finger pressure. Any of you doing this sort of reno would obviously have the lathe to do the work in so making a backing caul for the sandpaper would be fairly easy. But as sfclearwater will confirm it's a long and slow way to remove metal

Of course a headset doesn't spin like an axle does but we all want our headsets to have that smooth feel. Sfclearwater, you're obviously doing OK with your restored bearing cup but I wonder if it would have been that little bit smoother with a little better method.

I still wouldn't try this on a hub bearing cup or cone. There's still way too much chance of producing an egg shaped track even with a backing caul. On a headset with more bearings and no rotational speed to speak of there's no big risk of damage to having a ball or two come unloaded at some point. The others will carry the load. But a wheel axle has less balls and is seeing far more repetitive loading cycles. IF the cups and cones are not accurately circular to a much smaller tolerance the bearings would destroy themselves much sooner.
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