Gluing Aluminium

I have some cast aluminium garden chairs.
The screw holding one of the arms got loose and I forgot to tighten it.
Yesterday the top of the arm snapped off, leaving the screw in place.
I have the arm and the s,mall piece that snapped off.
The ends are clean and thankfully not shiny smooth but bright non-the-less.
I have gorilla clue, araldite and regular superglue.
Will any of those be OK or should I buy something else?
Reply to
Pinnerite
An epoxy glue like Araldite are probably best. Aluminium is a difficult metal to adhere to it is difficult to bond to the pure metal as it oxidises as soon as you look at it.
Richard
Reply to
Tricky Dicky
On Sat, 8 Aug 2020 12:23:11 +0100, Pinnerite wrote:
I would go for a two-part epoxy (so like Araldite) but specifically 'JB Weld', but only depending on what sort of stresses will be on the finished joint compared with the joint faces etc.
If they are likely to be great then it might be worth considering bracing (at the back etc) the joints with some other metal, also bonded to them with JB Weld.
Cheers, T i m
Reply to
T i m
But by definition is 'a filler' and so not likely to make a good butt joint in this case?
Good advice if it isn't a very clean a recent break already.
Except in this case it's 'cast' so probably wouldn't require any 'roughing up'.
Cheers, T i m
Reply to
T i m
If it takes any amount of force, e.g. from someone leaning on it, get someone to weld it, or brace and glue it. I'd use Araldite slow-setting were I gluing.
I have now idea what's permissible in NGs these daze, but could you put pics somewhere and post some means to find them?
Reply to
Chris Bacon
+1. It all depends on the area too. You are unlikely to be able to butt-join a thin cast section. But if it is such that you can bridge the crack and then fill the non-visible side with a good epoxy you might get away with it.
Reply to
newshound
With the forces likely on an arm against its mounting bolt I think there is zero chance of glue working. Either get someone to weld it or put a long steel strap around the end going at least a few inches up the arm on both sides and screwed, to reinforce the glued joint. If you don't mind what it looks like.
Reply to
Roger Hayter
+1. It all depends on the area too. You are unlikely to be able to butt-join a thin cast section. But if it is such that you can bridge the crack and then fill the non-visible side with a good epoxy you might get away with it.
I have decided to try the two part Gorilla. Welding is not possible.
Thanks for all the advice everyone.
Reply to
Pinnerite
Try Araldite, but there used to be a very noxious sort of glue that etched the oxide as it set, not sure what it was called though. Its probably banned now due to elf and safety. grin.
Seems a bit odd for it to break of, was it a casting? Could be it had some flaw in it all the time and if there is one, there could be others. Brian
Reply to
Brian Gaff (Sofa)
Yes if the casting is quite thick and is not suffering the porosity issue, a couple of self tapping screws in a brace on the hidden side might help with strength, ideally an angled section. Brian
Reply to
Brian Gaff (Sofa)
This is one of those instances where (for most of us anyway) 'a picture speaks 1000 words'.
Not that you couldn't describe the scenario to some degree but you would have to also describe the loads and stresses likely in the completed chair to predict the likely result.
Cheers, T i m
Reply to
T i m
But without a picture, we can make some simple statements.
Gluing pieces end-on won't work. Not strong enough.
------X X------- /
If you add a slab of material underneath, now there are a lot more square inches of glue working for you. But practical issues (how armrest fastens to tubular frame) aren't going to work out for you.
------X X------- /
XXXXXXXXXX ----------
*******
When the armrests on the chair I'm sitting in failed, I made new ones. The retention screws tend to constantly loosen up. But at least I have armrests.
Paul
Reply to
Paul
Of those only epoxy (araldite) stands the remotest chance of making a strong enough bond. I am somewhat mystified how a loose screw could make the arm snap off. I doubt you will be able to make a good enough bond to last very long in service unless you can add some strengthening as well.
Reply to
Martin Brown

By allowing excessive bending moment over the remaining material?
Whilst you may be right, it could all depend on what the loads are on the joint under correct circumstances?
eg. If the arm would only typically see load 'n' but with the screw loose, a part of the arm that may not normally carry much load got '10n' (causing it to fail). As long as the chemical bond will take the straight 'n' then all could be well?
Ideally, the break has happened at an angle to the normal load and hence mitigating the load on the repair joint to some degree.
Cheers, T i m
Reply to
T i m
On Sun, 09 Aug 2020 21:33:03 -0400, Paul wrote:

Well ...
But the OP said 'a small piece snapped off' and we don't know what load it would be under when it's repaired and all screwed up again? The bit that broke off may not typically be under much load at all and something like JB Weld on some clean breaks may well hold it perfectly?
Sure, if that was how / where it broke (hence the picture). ;-)
It might be that the op would reinforce the back of that area with a thin plate because the forces are only in shear, and as long as the screws are kept tight ...
Say the arm has a hole at each end that provides the main support (arm in tension) but a third /
smaller lug that *just* keeps the arm upright. The main tension screw becomes loose, allowing the full tension load on a part of the arm not designed for such and ...
Now, if you aren't into your structural engineering you (one) might not appreciate that and so assume the 3rd screw takes any real load in normal circumstances.
Loctite?
;-)
Cheers, T i m
Reply to
T i m

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