One way bearing press fit

LegendLength · Sep 18, 2018

I'm trying to understand the best way to fit a one way bearing (i.e. sprag clutch) to a 12 mm shaft. The sprag is CSK 12 ( CSK & CSK2RS Sprag Type Freewheel | Combined Bearing Freewheels | Sprag Type Freewheel | Stieber Clutch ). They say:

If units of standard clearance (C5) are used, the inner race should be fitted to a shaft of n6 tolerance, with the outer housing to N6 tolerance.

Using an online calculator it gives me a shaft diameter between 12.023 and 12.012 mm . Is it as simple as getting the shaft within that size range then pressing it on with a cheap hydraulic press?

And can I be confident the bearing won't slip under the rated torque (around 10 Nm from memory)?

They do have a keyway version but i'd like to stick to non-keyway if possible. Especially because I also have to put a sprocket on the outside.

Edit: Actually I'd like to use a keyway for the internal and press fit for the housing (sprocket). So please swap all that around above thanks.

CalG · Sep 18, 2018

loc-tite! It's your friend

Murf · Sep 18, 2018

As CalG stated above

LegendLength · Sep 18, 2018

Would that really stand the test in rough applications though? This will be a transmission taking a bit of a pounding.

CalG · Sep 18, 2018

LegendLength said:
Would that really stand the test in rough applications though? This will be a transmission taking a bit of a pounding.

If you can better qualify the tensile stress on the fit of the two metal parts, and give a "coefficient of friction" based on surface finish, We might concede that you may equal the bonding strength of the high strength Loc-tite. But even that is only due to the fact that the "fit" would expel any added loc-tite

In other words. Your reservations are as much warm air. If you don't KNOW better, It's the best option.

Murf · Sep 18, 2018

You would probably be amazed at what that stuff can do. They make many different versions for different things and of course, your fits of mating surfaces will probably be different if you use it. A true press fit, it would probably be almost worthless, but with a little clearance for it to get and stay between the parts, it really is some pretty good stuff...

LegendLength · Sep 19, 2018

Thanks for the info. I have some loctite 242 here. Does that sound reasonable to use on the prototype for testing?

Is epoxy a worse way to go?

CalG · Sep 19, 2018

LegendLength said:
Thanks for the info. I have some loctite 242 here. Does that sound reasonable to use on the prototype for testing?

Is epoxy a worse way to go?

Epoxy is a worse way to go

M.B. Naegle · Sep 19, 2018

LegendLength said:
Thanks for the info. I have some loctite 242 here. Does that sound reasonable to use on the prototype for testing?

Is epoxy a worse way to go?

Epoxy is just going to fill space. Loc-tite is made to bond to the metals but be just rubbery enough to cope with vibrations. Metal on metal joints still move due to vibrations and heat expansion, but epoxy doesn't (at least not at the same rates) so it will go on like it'll never come off, but a after a few hundred hours it could be reduced to powder. Loc-tite also doesn't inhibit future disassembly (though the red stuff requires heat).

WHHJR · Sep 19, 2018

Use loctite bearing mount compound not 242. Look it up at their website for the whole story. 242 is for threaded fasteners which have a much larger shear area than a simple cylinder.

2¢

winger · Sep 19, 2018

You may have to know what kind of oil is in the gearbox also to get the right Locktite. Made a difference in one of our assemblies.

Dave

Strostkovy · Sep 19, 2018

Are you by any chance building a ratcheting transmission out of sprag bearings? I always wanted to make a gokart that way.

john.k · Sep 19, 2018

Go with a keyed bearing if its going to take a pounding......IMHO,if you use an interference fit with a soft steel shaft,the inner race of the bearing will swage down the shaft ,and change the fit .Key and loctite.

LegendLength · Sep 20, 2018

john.k said:
Go with a keyed bearing if its going to take a pounding

I want to still use a key for the internal part. I am having trouble finding 12 mm shaft with a keyseat surprisingly, they're all imperial. I'm thinking of trying to grind a woodruff onto the shaft for testing using a hand grinder, hopefully that will hold with some loctite.

Virtually all sprags seem to be metric, otherwise i'd just go imperial.

john.k · Sep 20, 2018

I was referring to the inner race.....dont you have a lathe? you can easily cut a keyway with any lathe........Alternatively,take the shaft to an engineer,and have the keyway cut.

LegendLength · Sep 20, 2018

Don't have any tools like that unfortunately. Spoke to a few local shops but none of them could help except one who wanted to charge nearly 100 AUD. Will keep checking online for other shops who might post it and do it cheaper.

Alternatively it will probably be cheaper to buy a cheap ebay shaper because i need to do many of these in the long run. I still don't know if they are useless or not in that regard though (for 12 mm shaft, 4 mm keyseat).

eKretz · Sep 20, 2018

Yeah the right stuff for bearings is either amber or green colored (which depends on application) in my experience. Get the right stuff.

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One way bearing press fit

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