I was working on a M20 gearbox yesterday and found that the outer ring of the main bearing is able to turn round in the housing. There is no play, but it just isn't stuck
I can't rebuild the box like that.

What can I do about that ?

- use Lock tite ?
If so what number of Lock tite and does it really work ??? Is it safe ??
Anyone with experience ?

- or is there a way to shrink the housing just a little bit ?

Loctite do a bearing lock, takes up larger gaps. Works well.

I've used Loctite successfully in the past on housings that have shown signs of fretting or movement. It seems to work well.

641 seems to be the current 'standard' bearing fit. I think you'll need to clean everything off properly and then check how loose it is.

Yep LOCTITE bearing fit - clean everything with solvent (not petrol) and perhaps abrade with some fine wet and dry.
BUT - i find, that other than on wheel bearings and such, its not very permanent - perhaps heat/oil ?


If really slack - place three sections of 0.0015" feeler gauge + loctite, hammer bearing in and sell..............
I know- i bought a frame with the head races fitted that way (metric instead of imperial ?)

Hi Mick,
The best two grades to look at would be Loctite 638 or 648. Both are a high strength retainer most suited to high temperature applications.

Clean both parts first, apply and leave to set for appx 1 hour when assembled.
A tip would be to keep the tube in the fridge. Anaerobic adhesives can go off if kept long term. On a warm sunny window sill will see it go off quickly. But in a fridge would mean that it should keep for years and still be fine.
When it has gone 'off' though, it does not really look any different so it's good to test an old bottle first or people just blame the product.
Hope that helps you
Darren

email (option): Dwrudd at lineone dot net

Hi Mick..Contact me off forum...Ian

email (option): ian@wright52.plus.com

And there are two other ways to approach this.
1) Speedi sleeve which is just what it sounds like, a sleeve that fit around the bearing thus making it bigger
2) davcon aluminium putty.
Take a few thou of the outsid of an old bearing to use as a former then fill the gap with davcon.

email (option): bsansw1@tpg.com.au

I thought Speedi sleeve was for worn shafts? But works for housing as well apparently.

SPEEDY SLEEVES - I assume these are the crinkly shim steel 'cups' i have - given many decades ago as a free sample?
Didn't know they were still out there but i have used them many times - usually when fitting metric bearings into imperial frames for specials and the such.

They work extremely well - BUT like Loctite retainer, require a substantial clearance between bearing and housing to work well.
(i think loctite recommends a gap of 0.2-0.5mm MIMIMUM).

Often the clearance is much less than recommended by Loctite - which is the problem ...



As for using shims to pack out a bearing, like knurling pistons and shafts to make them bigger - very un-engineering but very period. A friends 1st car, in the late 1960's - a Ford 100E, had knurled pistons in it !!!!!



Welding can be used to shrink metals - usually steel to get bearings out of housings.
High silicon pistons can be 'grown' a few thou. bigger by baking them in an oven (done this many times with model plane/boat engines)

You are correct nig. Speedi sleeves are indeed made for a repair to a shaft when a seal has cut into it over time. Not recommended for a housing repair or shaft shim on a bearing. If the unit can be dismantled, then a good repair would be to alloy weld and turn back out to size but that rarely happens, so Loctite really is best bet, if it spins freely in hole, then you can assume a couple of thou wear which is good for Loctite which is listed at 0.25 MM. Max not minimum. Anything more than that really weakens the bond.
There is a product that looks like solder but you can melt it into the casting with the bearing in place and the bearing will pull out later. I have used it to repair a thread in alloy the same by leaving the stud in place and running the 'solder' into the threads, you then let cool and unscrew with a spanner. I have yet to try it on a bearing but can see an experiment coming up !
Darren
Ps. Can't just remember the name of the stuff as its on my desk at work, but if anyone is interested I will post it tomorrow on here.

email (option): Dwrudd at lineone dot net

Hi Mick..Contact me off forum...Ian

email (option): ian@wright52.plus.com

A friend of mine had the same issue with the crankcase for a A65 and got told by an engine rebuilder that the reasonable thing to do was to hard-chrome it. But more stress from a cranshaft I assume.

email (option): bsansw1@tpg.com.au

Hi Trevor,

Nearly, the one I was thinking about is Alutight, similar to Lumiweld, but I have found it much easier to use.
I met the guy (Bjorn) at Stafford Bike show last year and he does a pretty neat little demo. Very easy to use and I have found it to be spot on.

I think you would need to use the old bearing as a form for the job as you say, but may be worth looking at as a permanent fix.
Darren

email (option): dwrudd at lineone.net

Or you could replace the gearbox case altogether...Ian

email (option): ian@wright52.plus.com

Haha. Trust you to show up with the common sense approach

No wonder my life is too complex

Darren

email (option): Dwrudd at lineone dot net

Ian Wright

Or you could replace the gearbox case altogether...Ian

email (option): bsansw1@tpg.com.au