Bearing Fits?

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mcostello
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Re: Bearing Fits?

Post by mcostello »

You would not think that I EVER used Locktite to fix a very slightly mismatched bearing fit, would You? Ha Ha Ha Ha Ha Ha!
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BadDog
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Re: Bearing Fits?

Post by BadDog »

I've use the green stuff, 620 and 640. Good stuff when you must, but I prefer a mechanical fit. As I understand it, that is also important for proper internal loading for the bearing to last.

In fact, one of the things that pushed me into learning and doing my own machine work was a the last job I hired a "machinist" to do. I was changing out the common "small bearing" GM NP205 input to the larger bearing found in some HD GM applications as a 32 spline input, but very commonly found as an almost as strong 31 spline input in 70's to mid 80's Ford F250s and bigger (and others, but close enough). Anyway, the bearing is substantially larger for those input shafts, so I hired a local shop with a good rep to machine out the case for the large bearing. "Sure, no problem, I do this all the time". And I gave him the bearing to fit. When I picked it up, the bearing would just fall through the hole! I think I could have lobbed it across the room and have it fall through! Ok, that's a gross exaggeration, but I wasn't happy. He completely blew it off, and now tells me "happens all the time, just use bearing retainer." The best I could get out of him was "bring me another case and I'll do no charge". Why? You buggered up this one, why would I give you another to screw up!? We didn't part on very good terms, but they are still "highly regarded" in the local off road crowd. Whatever...

Anyway, I did use that case with the thicker "gap fill" green bearing retainer (fills up to 5 thou IIRC) to build my compound reduction "doubler", and it held up in my Rock Crawler for the several years I ran it. I'm just glad it was a trailered rig as I wouldn't have trusted it for long trips. And I sure didn't want to use that in my friend's flywheel pilot, particularly with the temps it may see behind a turned up 6BT that easily accelerates a close to 9K gross curb weight outfitted Sub plus occupants to highway speeds as easily as a typical Muscle Car. I plan to use it to hold a motor bearing that is too loose in an end plate, and I've used it with seal surface repair sleeves, etc; certainly has a place in my shop.
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Bill Shields
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Re: Bearing Fits?

Post by Bill Shields »

misconception...life of a properly designed bearing application has nothing to do with the fit.

many designs / fits are being geared AROUND using the stuff

go to a modern auto assembly plant and watch....
Too many things going on to bother listing them.
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Harold_V
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Re: Bearing Fits?

Post by Harold_V »

Bill Shields wrote: Wed Jan 24, 2018 7:40 am misconception...life of a properly designed bearing application has nothing to do with the fit.
Depends. Fit, when too tight, will definitely affect bearing performance and life. That's one reason why using glue could be of benefit.

It's cheaper to use glue than to uphold rigid tolerances. I expect that's one of the reasons it is used as you suggested (go to a modern auto assembly plant and watch....)--not that it's necessarily better.

H
Wise people talk because they have something to say. Fools talk because they have to say something.
mikeehlert
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Re: Bearing Fits?

Post by mikeehlert »

warmstrong1955 wrote: Tue Jan 23, 2018 12:34 pm That's what I do Russ.

I used to get a lot of work done at the local machine shop when I was still in the underground biz. Invariably, he always asked if I could bring him the bearings, pins, or whatever when he did jobs for me. Got the same requests from machine shops from Arizona to Alaska too.
A lot of merit for doing that I think!

Bill
Mechanical Engineer here. Got my start designing stuff in some very high end business's. If I sized a bore for 0.5005 to 0.5010, that's what I got. I knew the C'Less ground shaft was going to fit.

Then I got into the rest of the world. Was always a bit annoyed at the machinist for wanting the matching purchased parts before he did the job. Boy did he show me some things. Always, always have the fitting part in hand, measure it and eyeball check it for size before making those last couple passes. Saves me lots of time now that I am doing my own work and the trash can is not nearly as heavy.
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liveaboard
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Re: Bearing Fits?

Post by liveaboard »

There are also bearings made with a greater unloaded tolerance, intended to work correctly after being compressed by being pressed tight.
Yes, there are proper numbers and terms for all that but I'm not going to pretend I know what they are.
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