Bearing fit

I am staring to build the Myfordboy's hacksaw.

My first proper project. Expect quite a few questions to come...

My first one regards the fit of a bearing - both into a housing and onto a shaft.

I far as I can understand, the published tolerances are in a few um for small bearings. I cannot even measure down that small.

Would an acceptable approach be to machine to allow an easy press fit by hand then fit with a retaining compound like Loctite 641 or is there a better way?

Yes Ian, that's certainly the approach I would take.

David

641 ‘Bearing Fit’ is wonderful stuff !!

MichaelG.

That was fast!

Thanks.

Loctite 601 or 638 are quite fast curing, but if you need more time to assemble things, then 620 is your best bet.

It’s an easy answer !!

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Be that as it may ... but why wouldn’t you use ‘Bearing Fit’ for fitting bearings ?

MichaelG.

I will start you off easy - they will get harder.

Loctite 601, 620 and 638 are part of their extensive range of BEARING FIT PRODUCTS.

Edited By old mart on 18/10/2019 17:11:41

If you had a high temperature requirement then 638 will retain its strength for longer than 641 and 648 will be even better at higher temps.

638 will also tolerate a larger gap than 641 which may be handy for poorly fitting parts or where a housing has become worn.

Or like a lot of people who may not need to fit bearings very often they may just reach for what they have on the shelf rather than pay for a bottle if it is a one off job. 638 is also less likely to need an activator on passive materials then 641 so no need to buy activator.

Edited By JasonB on 18/10/2019 18:57:29

Thank you for not ‘shouting’ Jason

I agree that, according to the circumstances [*] all of the products you mention may be viable alternatives to ‘Bearing Fit’ ... but for the job that Ian is contemplating, it does seem the obvious choice.

MichaelG.

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[*] BMW for example specifies 638 for retaining certain bearings on the Superbikes.

I am a big fan of 638, it cures quite quickly probably too quick if you have adjustments to make but in some assembly situations the speed can be a bonus. It has good gap filling up to 0.25 mm if I remember correctly and the cured joint is extremely strong. For permanent fixing and retaining of parts 638 is the one I always use.

.

Likewise, Ron [for several decades]

But I maintain that ‘Bearing Fit’ is generally more appropriate for fitting bearings.

MichaelG.

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Edit: Quoting from the 641 Technical Data Sheet:

“LOCTITE® 641 is designed for the bonding of cylindrical fitting parts, particularly where disassembly is required for service operations. The product cures when confined in the absence of air between close fitting metal surfaces and prevents loosening and leakage from shock and vibration. Typical applications include retention of bearings onto shafts and into housings.”

Edited By Michael Gilligan on 18/10/2019 22:03:46

Treacle works too. But takes a bit longer to set than Loctite.

The area of the inner and outer surfaces can be considerable. Clearly a properly operating bearing requires “support” so needs a gap-filler when shafts/housings are out of spec.

Some consideration of this and the need to dismantle might be far more sensible than reaching for the strongest, most permanent offering available as the ‘dumb’ option for any and every instance a problem may arise?

Well-said, ndiy

MichaelG.