JB Weld

[Bigplumbs]

I have a very small crack in the ali gearbox on an outboard I an working on for myself. It is only about 25 mm long and very thin. I know the correct way would be to have it ali welded but that is problematic.

Has anyone successfully or other wise used JB Weld as below

https://www.amazon.co.uk/dp/B007PP26RI/ref=pe_27063361_485629781_TE_item

 

[Hurricane]

I know someone who mended an old car cylinder head using JB weld.
I think it lasted a year or so before he scrapped the car.
So, I guess it works.
You probably have to toss up whether the project is worth all the hassle of getting it welded properly.

 

[footsoldier]

I have used JB Weld for a number of repairs over the years, always successfully.

However two points arise:

I do not recognise the example in the illustration. The type I have used was a two-parter in tubes - bit like original Araldite - mixed in equal proportions. It may be that like many other products the range has expanded. It would be as well to check all the variants to establish what is most suited.

The 'original' JB Weld I used would be difficult to introduce into a thin crack such as you describe due to its composition. I suspect you would need to grind it out somewhat before introducing the product.

 

[davidej]

I use the two part and to get it to penetrate into cracks, I warm it all up with a heat gun. But the crack has to be clean, which it won’t be if it has been underwater, so grinding out is probably necessary.

 

[Scubadoo]

No experience with JB weld, but I made an aluminium repair recently with Teroson chemical metal and it seems very effective repairing metal cracks etc.

TEROSON UP 130

 

[greeny]

Sorry guys I'm going a little off track here but it is relative to the use of JB weld.
I've just dropped my swing keel out and the play in it is partly due to the top Pin and bush that it swings on.
The pin in the bush is ok but the bush in the keel has worn a bit. I was going to open up the 30mm hole and get an oversized bush made to 34 mm O.D.
Then thought that resetting the original bush may be possible using JB weld. There is a lot of pressure at this bearing so I'm not sure whether this would be successful or will the JB weld "crumble". Has anyone used JB weld in a "sructural," weight bearing situation or is it just for hole repair type application?
I'm not looking for a bodge here, the repair needs to have longevity but I'm not into doing extra work for no reason.

 

[limecc]

@Bigplumbs Sorry to hear about this. You could get half dozen genuine Durafix rods from Amazon. They are amazing and flow at low soldering temps. But not if you get the Chinese knock-offs from ebay which don't compare. Probably best to use MAPPgas if you've no access to oxy/acet.

https://www.amazon.co.uk/Durafix-Aluminium-Welding-Easyweld-Brush/dp/B00GG09068

 

[KevinV]

Sorry guys I'm going a little off track here but it is relative to the use of JB weld.
I've just dropped my swing keel out and the play in it is partly due to the top Pin and bush that it swings on.
The pin in the bush is ok but the bush in the keel has worn a bit. I was going to open up the 30mm hole and get an oversized bush made to 34 mm O.D.
Then thought that resetting the original bush may be possible using JB weld. There is a lot of pressure at this bearing so I'm not sure whether this would be successful or will the JB weld "crumble". Has anyone used JB weld in a "sructural," weight bearing situation or is it just for hole repair type application?
I'm not looking for a bodge here, the repair needs to have longevity but I'm not into doing extra work for no reason.

I've attempted a similar thing on a brake lever on the quad bike. It worked briefly, then crumbled - I would look to a solution with more longevity for an awkward to get at part like yours.

 

[limecc]

I've attempted a similar thing on a brake lever on the quad bike. It worked briefly, then crumbled - I would look to a solution with more longevity for an awkward to get at part like yours.

You must have had a crazy moment attempting JB weld on a critical part like that.
I would trust a Durafix repair though.

 

[VicS]

I have a very small crack in the ali gearbox on an outboard I an working on for myself. It is only about 25 mm long and very thin. I know the correct way would be to have it ali welded but that is problematic.

Has anyone successfully or other wise used JB Weld as below

https://www.amazon.co.uk/dp/B007PP26RI/ref=pe_27063361_485629781_TE_item

You dont need the high temperature version in your link for an outboard gearbox ......... they are water cooled!
The "original "version would be suitable
Or the marine version if you can obtain it

The difficulty will be getting the surfaces oil free if the crack is into the oil filled part. You might also need to widen the crack before filling

 

[The Q]

yep, use the two part semi liquid JB weld in a tube, so it will get into the crack properly, the semi hard stuff originally shown above won't get all the way into the Crack , I've used both in the past. you'll probably have to tape up one side to stop it running out..

 

[julians]

to avoid all the issues of getting the jb weld into the crack and ensuring the crack is fully clean etc etc, could you fabricate a small aluminium patch that is bigger than the crack, and then use jb weld to 'glue/weld' the patch over the crack, and therefore sealing it up?

This would be much easier to clean the surfaces for etc - might not look as nice though.

 

[limecc]

I'm struggling to understand the resistance to a proper repair. Only casualty is the paint. Any competent DIY'er with a blowtorch can do a Durafix weld, why use a sticking plaster?

 

[Daydream believer]

Sorry guys I'm going a little off track here but it is relative to the use of JB weld.
I've just dropped my swing keel out and the play in it is partly due to the top Pin and bush that it swings on.
The pin in the bush is ok but the bush in the keel has worn a bit. I was going to open up the 30mm hole and get an oversized bush made to 34 mm O.D.
Then thought that resetting the original bush may be possible using JB weld. There is a lot of pressure at this bearing so I'm not sure whether this would be successful or will the JB weld "crumble". Has anyone used JB weld in a "sructural," weight bearing situation or is it just for hole repair type application?
I'm not looking for a bodge here, the repair needs to have longevity but I'm not into doing extra work for no reason.

Why not use an oilite bush? Drill to a slightly smaller size then enlarge to the correct size. If that becomes expensive in core drills (I assume you would use those) you could research the different types of loctite & find one that will really glue the bush in place. You may find a core drill close enough to allow you to enlarge the hole with a mini grinder. Remember that oilite bushes are oil filled so may not accept adhesive. However, you may set the bush in some JB weld to allow it to "bed" evenly, provided you have a fairly close fit to start with.
There are a number of suppliers of bushes. One is bearing boys but I have seen some with a much wider range at an economical rate. . Note that if the outer diam is too big for the inner diam, you can always put one smaller bush inside a larger one. In your situation you are not spinning at high speed & the side movement will be retained by the casing.
Oilite

 

[Restoration man]

I’ve used jb weld with good success many times , if it were me I would open up the crack a little not all the way down with dremal and feather out around the crack a bit as well , and get very small drill like 1mm and drill a load little holes (not all the way through the casing ) around the repair, and clean very well acetone or alcohol, keep the jb weld tubes on the radiator to get nice and warm and runny ,mix up and slap in , I think that should work , it has done for me lots times in the past

 

[penfold]

I'm struggling to understand the resistance to a proper repair. Only casualty is the paint. Any competent DIY'er with a blowtorch can do a Durafix weld, why use a sticking plaster?

Probably because a casting the size of an outboard gearbox casing would need a very large gas torch which most people do not have. Correctly applied epoxy is as proper a repair as durafix might be.

 

[Bigplumbs]

Some very interesting and useful answers there.

I have tried the ali welding before and I have failed every time. No idea if I got the original rods or the Chinese knock offs but then how do you ever know what you are getting these days. I also don't want to strip the gear box completely down and fear the amount of heat you would need to make it rub correctly.

The crack is very small and I don't even know yet if it goes all the way through. When it is not raining so much I will investigate further.... No real hurry on this one.

I rather like the idea of cleaning up the area and using a patch. I think I will try this on a piece of ali that I deliberately make a crack in and fix it in this way and then stress test it .

 

[limecc]

Probably because a casting the size of an outboard gearbox casing would need a very large gas torch which most people do not have. Correctly applied epoxy is as proper a repair as durafix might be.

Speaking as a qualified former engineer, have to fundamentally disagree with your statement. Durafix is actually stronger than the base alloy. Belzona, JB weld or whatever, there's no comparison. Durafix is blend of metals, not a resin. It will never separate or crack and it's a harsh environment which caused the crack in the first place.

If the repair were mine, I'd pre-heat the casting in an oven and use oxy/propane because that's what I've got, otherwise a 400g cartridge of Mapp gas costs £10 and fits the majority of plumbing torches. Only need to reach 390°C, barely more than needed for soldering copper.

 

[Bigplumbs]

Speaking as a qualified former engineer, have to fundamentally disagree with your statement. Durafix is actually stronger than the base alloy. Belzona, JB weld or whatever, there's no comparison. Durafix is blend of metals, not a resin. It will never separate or crack and it's a harsh environment which caused the crack in the first place.

If the repair were mine, I'd pre-heat the casting in an oven and use oxy/propane because that's what I've got, otherwise a 400g cartridge of Mapp gas costs £10 and fits the majority of plumbing torches. Only need to reach 390°C, barely more than needed for soldering copper.

Not sure if I would be putting the whole lower half of the outboard leg including the drive shaft into the oven. And I aint stripping out the whole gearbox.

I knew a bloke once who had a crack in his house extension and decided to dismantle part of it and rebuild. All that was required was wait till winter when the clay was saturated again pushing up the building and then a little filler

Going over the top and 'doing it properly' is not always the best route

 

[KevinV]

You must have had a crazy moment attempting JB weld on a critical part like that.
I would trust a Durafix repair though.

I was only bushing a worn hinge point, and it's a farm quad, not a racing machine