Bearing fit up

[Welderpaul]

I have a slightly worn shaft that measures 18.9 OD on average, it is slightly out of round and a little worn where a previous bearing has spun.

The hole into which the thrust bearing goes look ok and measures at 41.2mm.

The nearest bearing i can get is 41.6 OD which should be a tap-in fit, but is 19.1 on the ID.

I know the ID isnt too far off but i'm bothered about it spinning again. Its a hand-windy handle so no speed on it (Levelling box handle), but the way it is at the moment the centre shaft spins inside the bearing and doesnt even touch it. The bearing is fairly chewed up inside but luckily the bearing seems to have taken the majority of the damage rather than the shaft. The shaft measures differently on its diameter depending where you measure so difficult to get an accurate dim.

I can't weld the shaft, and no real machining facilities. Is there a quick fix way of ensuring the shaft doesnt spin. I can put retaining compound in there but don't put much faith in 'non-mechanical' methods.

It's a pain to get back into once the thing is back together and if it spun, i wouldnt know until it jammed up.

What about forming some 'pips' with a chisel or similar on the shaft to get it to bite? Bodging territory? Hmm.

 

[madkayaker]

Build up with chemical metal then file round?

 

[Hitch]

What about forming some 'pips' with a chisel or similar on the shaft to get it to bite? Bodging territory? Hmm.

A Couple rings of heavy centre dots and a bit of loctite has got me out of trouble before

 

[rory1]

I appreciate you said you have no machining facility's but a good deep knurl would maybe bring the diameter out enough for a light duty load on the bearing ....

If the diameter is out of round you have nothing to loose by bruising the shaft with a series of big centre punch marks. This is quite common practice if your up against it!

 

[wyn]

I once repaired a shaft by internaly machining two clamped aluminium blocks to the diameter needed for the bearing to sit on.

The shaft was then coated with good quality chemical metal and the two aluminium halves coated with release agent and clamped around the appropriate bit of the shaft.

A day later the clamps were removed and the excess chemical metal tidied up a bit leaving the shaft built up to the right diameter for the bearing.
It was on a supercharger type blower, blowing fine dust up into a building....it lasted a good few years of 8 hours a day running.

 

[Pete.]

A Couple rings of heavy centre dots and a bit of loctite has got me out of trouble before

Yup this works very well. It's a time-proven method of fixing small bike main bearings onto crank journals when the fit is becoming loose enough toallw the inner race to spin. I've done it several times and it has always worked beyond my knowledge of longevity.

Welderpaul - you should update your knowledge of non-mechanical and chemical fixing. Especially for a hand-crank type repair it would be ideal. If the gap really is too big for a chemical repair, it should be big enough for a shaft repair sleeve/speedi sleeve.

EDIT: just read this:

The hole into which the thrust bearing goes look ok and measures at 41.2mm.

The nearest bearing i can get is 41.6 OD which should be a tap-in fit,

That ain't happening. Interference fits are 1 and 2 thou, you're not getting a bearing in a hole 16 thou smaller than the OD.

 

[adamsmitqc]

what type of bearing is it? you have to carefull when the outer race of bearing is an interference fit, not enough clearance and you lose all clearence in the bearing and it wont last.

there is a possibility of using a smaller bearing on a tapered adapter sleeve. easy to fit but you will need enough room for the sleeve when measured horizontally along the shaft and also the washer a nut which pull it onto its taper.

Any pics of the setup would help/

 

[normspanners]

+ 1 for centre pops but if you wanted a 'proper fix' you could take it to an industrial chromer they can build up to quite a depth then grind back to whatever you need, I have repaired several hyd cyl rods in this fashion. One very old ram in particular we could not get the seals of a particular imperial size so had the rod chromed up considerably to the next size metric seal and machine the end bushing to suit. it was still cheaper than turning a new rod and bushes

 

[brightspark]

I appreciate you said you have no machining facility's but
If the diameter is out of round you have nothing to loose by bruising the shaft with a series of big centre punch marks. This is quite common practice if your up against it!

as said above and use locktite .the only way that will come loose is with heat from a blowtorch

 

[Welderpaul]

That ain't happening. Interference fits are 1 and 2 thou, you're not getting a bearing in a hole 16 thou smaller than the OD.

1 thou = 0.0254 millimetres?

 

[MattF]

1 thou = 0.0254 millimetres?

Yup. You have a 0.4mm difference, hence near as owt 16 thou.

What exactly is it that you're doing? Couldn't you just whack an oilite bush or similar in there instead?

 

[AndyStobbs]

Could you get a bearing type where the inner race has a shaft collar incorporated onto it, they usually have a grub screw for nipping onto the shaft.

 

[Welderpaul]

So a thou is nigh-on one 40th of a mm? 2 thou an intereference fit? Thought it was more than that. 40th of a mm is nothing

 

[adamsmitqc]

1 thou = 0.0254 millimetres?

Yep... Rough rule of thumb is 40 thou to a mm, 4 thou to 0.1mm etc

 

[MattF]

So a thou is nigh-on one 40th of a mm?

Yup. Just a shade under.

2 thou an intereference fit? Thought it was more than that. 40th of a mm is nothing

Depends on the material to some degree, but 0.4mm is quite a large chunk when you're trying to bash something in there.

 

[MattF]

Could you get a bearing type where the inner race has a shaft collar incorporated onto it, they usually have a grub screw for nipping onto the shaft.

These the type of thing you were thinking of?

http://www.bearingboys.co.uk/SKF_Bearing_Inserts-3656-c

 

[Pete.]

Depends on the size too, and although a 40th of a mm (1 thou) might seem like 'nothing' it is enough to stop your bearing fitting easily. 16 thou is a country mile.

Valve seats were/are often fitted with 2 thou interference, and they don't fall out so often.

 

[AndyStobbs]

These the type of thing you were thinking of?

http://www.bearingboys.co.uk/SKF_Bearing_Inserts-3656-c

Yes those. Paul is after a thrust bearing though I think.

 

[Welderpaul]

Yes, a good idea but one of those wouldnt fit in there unfortunately. The size i need isnt in any of the catalogues. I've just been out and measured it again and i'm right with my sizes.

I wonder if they were made as specials for Fordson (1958 if it is the original bearing)

 

[Pete.]

The hole into which the thrust bearing goes look ok and measures at 41.2mm.

That's inch and five eights, so the original bearing was 3/4"ID and 1 5/8" OD. I would work on finding a bearing of those dims and work on making the shaft fit the ID.