I need to secure a boss made from aluminium rod into a hole made in the wall of an aluminium tube. Of course welding would be ideal - but there's little load on it. And I'm not sure I can be bothered finding an aluminium welder. Unless I could do it myself with my MIG. Which I'm not much good with on steel. ;-) Car body filler? Epoxy? Any special precautions?
Wouldn't be worth buying a roll of aluminium welding wire for one small job like that but yes you could do it with a MIG with the right wire. If you want it welded and it's small enough to post a mate of mine could TIG it for you. I've got to get some other stuff to him soon anyway so it could go in with that. Otherwise roughen the surfaces up a bit and araldite it. That'll be as strong as you can get short of welding it.
=A0 London SW
Brazing if you've got a MAPP torch?
=A0 =A0 London SW
Then again, maybe not...
In message , "Dave Plowman (News)" writes
Hi Dave, I have never tried this, but a friend of mine had some success with the following style of product. I thought of giving it a try just to see how easy, or not, it would be. More like soldering/brazing than welding.
Car body filler? Ugh!
Provided there is no peel stress, epoxy gives an extremely strong bond. Araldite always used aluminium to aluminium bonds as the standard against which other bonds with their adhesive were compared on their data sheets.
Colin Bignell
I seem to be always buying stuff for that 'one small job' - given the hassle of getting anything like that done round here. I have enough materials to make the whole thing again a couple of times - so it wouldn't be a disaster if I fooked it up.
Thanks - but I was hoping to get it finished tomorrow. ISTR seeing ally welding wire in Halfords - might be worth having a go. I'm sure if successful the rest would get used sooner or later.
It's only holding an air temp sensor. BTW, you were right about the thread being M14 1.5. Got a set of taps off Ebay for pennies which did the job just fine. Only carbon steel, but ok for ally.
If load really is low, PVA works well on ali
NT
Dave Plowman (News) brought next idea :
The slow setting epoxy, roughen then score the surfaces first.
Araldite will be fine then. Build up a bit of a bead of it round the join for added support and it'll be in there till doomsday. If the boss had a little groove round it for the araldite to lock into so much the better but some good deep scratches with a file or chisel edge should do.
I was told when I worked with a group that developed composite structure for aircraft that epoxy glued aluminium degrades fairly rapidly over time and that over-the-counter epoxy gues really don't bond well to aluminium. The preferred adhesives for aluminium are a hybrid epoxy adhesive such as epoxy-nylon and specialist polyurethane glues. Some of these glues require special primers or activators to be applied to the surface before bonding.
If I wanted to make a permanent job I'd braze it, using the appropriate aluminium brazing rod.
Thread the tube, tap the hole? Or are the taps/dies too small?
I was building a control panel of Aluminium recently which had plywood inserts and decided to try ordinary polurethane wood glue - 5 minute setting gunable type . Totally successful. I then needed to attached a small Al bracket to carry a connector and again used this PU glue, finding it did the job perfectly for an Al to Al bond.
Now having read the above post about epoxy glued aluminium degrading over time, I'll might remember to have a look in a year's time to see if the bond is still OK.
Rob
Liquid metal/JBweld/Carbody..roughen and degrease..and clean.
If you have the right flux, you can soft solder it too.
I have some of that..its really odd to see ordinary solder wetting 'tinfoil'..
It needs to have a reasonable seal which means a flat surface. (the sensor goes at right angles to the tube to measure the temperature of the air passing through the tube) And a thread in thin walled tube wouldn't be satisfactory.
De-grease, abrade to remove oxidised layer, degrease again, then Araldite.
They stick aeroplanes together with it, so maybe it's good enough for sticking a sensor. ??? =-O Cheers Don
I think the problem with epoxy is that the epoxy is porous to oxygen, so the aluminium oxidises beneath the epoxy and that causes the strength of the epoxy/aluminium bond to decrease.
If I do decide to have a go at welding with my MIG - what would be a good starting point current wise, etc?
The tube is approx 70mm diameter with a 2mm thick wall The bush 24mm x 12mm with a 14mm thread already tapped in it.
Here's a nice article about the way that Lotus stick the Elise chassis together from bits of aluminium - they use a specialised epoxy resin.
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