A useful little repair process this one that can be applied in all manner of ways to solve different problems. Basically, this was what we did before they offered proprietary glues and compounds like 'Liquid-Metal', and you can use it pretty much as you would those kind of metal glues. Its tough, sets like metal, & can be filed, drilled or tapped like aluminium. It can withstand heat almost as well as aluminium, and most solvents; even hot oil.
Making the epoxy/aluminium composite yourself, you have a lot more control over the consistency of the mix, making it more versatile still, while using regular 'Araldite', its a LOT cheaper than proprietary equivalents, and saved having hundreds of different tubes of glue, knocking around, leaking, going hard in the tubes, before you use them up!
So, to business! In this example, we used the loaded epoxy repair technique to rebuild a cracked mounting boss on the starter motor for Donna's 'Pup'. How it got broken in the first place is any-ones guess; probably over tightening the mounting bolt, or trying to remove the starter with a lump hammer or something! Doesn't matte, problem is that the boss around the bolt hole has cracked off and we need to build it back up again so that the bolt has something to press against and not bend, only pressing on one side.
Before ^. After V
Before & After pics, so you can see what we are at. Basically, gloop some 'stuff' around the broken chunk of metal, let it set, file and drill to shape!
WHAT YOU WILL NEED:- Epoxy Adhesive (Resin + Hardener); Aluminium Filings (To 'load' the epoxy)
First job is to make some fine aluminium filings! The higher the % of filings to glue, the more 'solid' and less plastic the material will be when set. Simple operation, grab a chunk of scrap aluminium, a file, and an old tea-tray, and file away as much metal as you need!
I had conveniently to hand a bit of extruded Ali support rail that had been hacked up off 'the heap' and made my filings from that. Old engine cases, bits of old green-house, pretty much anything you have to hand that would go in the recycling box, can be used. But once you have filed down a volume about equal to the volume you need to build up, you need to gather it up and put it in a suitable receptacle, like an aerosol lit, to mix with the glue.
But first you need to prepare the artefact you are going to 'gloop'. The area that's to be glooped needs to be properly cleaned so that the glue will stick to it. If its not bare metal, it may need wire-brushing or grinding back to get a good surface to work on, that the glue can 'key' to. Then, you may need to mask around the area to be glooped, first to stop the glue going places you dont want it, but also to contain the glue in the region you want to build up. It will be runny, and it takes a while to cure, and in that time, it can often run, leaving you with little or no material where you want it!
Then you can mix the gloop. As a rough guide, about 50/50 glue to filings. Its often best to put the glue in one tub, then add the filings to suit, rather than the other way around. Mix until you have a thick, even consistency, the resin and hardener thoroughly mixed, and the filings well wetted in the liquid.
then using lollipop stick or other suitable application tool, gloop the mix over the area to be built up!
Allow to cure. Instructions for the epoxy should give a rough time for how long this should take, and loading the mix with filings shouldn't REALLY alter that, but its worth giving about 50% extra time to be sure its properly hardened.
After allowing to cure, check you have enough build. Sometimes during cure the gloop flows, or settles, or finds crevices to flow into, leaving your area short of material. No great problem, you can give it a second application if needs be, either before working, or after. In fact, some-times its easier to build up in stages, shaping between each build.
Once you have sufficient build, and the gloop has fully cured, it can be worked with conventional hand tools, to dress off any excess, and shape to your own satisfaction!
NOT the appropriate way to use an electric drill! Photo was 'staged' so you could see the bit coming out the back of the boss where built up! Proper way to do it is on a solid surface with a block of wood beneath! (which was how I actually DID do it, BTW!)
All shaped & ready to go! (Repair can be tidied up / disguised by painting, if needs be or left bare)
That is the principle of the technique, apply it as you wish. Yes, not a LOT different to what you can do with proprietary resins, and they can be more convenient. But this 'old fashioned' way gives you a little more versatility, using more or less aluminium, or depending on the part, iron filings, or perhaps even bronze or copper.
Using the same technique with bronze, its possible to repair or make 'low stress' bushes, for things like gear-lever pivots, or control levers, for example.
I have also used the same technique quite successfully on engine cases, where bosses or lugs have been chipped or broken, also on casings like the clutch or magneto covers, where they have been 'holed' or cracked by a drop. (quite a common one when I was riding comp-trials! If there was a rock, when you fell of, almost certain the oil holding clutch cover would find the sharpest bit of it, when you fell off)
That leads into slightly more involved techniques of resin repair, where phenolic, or GRP resin can be used instead of epoxy, for a more brittle plastic / metal composite, and for areas like casings where a smooth oil-tight finish is wanted, a 'tri-matrix' composite, using fibre-glass tissue to support the loaded resin. Getting REALLY clever with the stuff, its even possible to cast small parts out of the stuff.
Basically, with a little know-how and a feel for the materials, what can be done with resin composites is pretty incredible; might seem a bit botchit & scarper, glooping araldite over stuff, BUT, this is ACTUALLY pretty high tech stuff! Its only a small step from the exotic high-tech composite materials used in aerospace & motor-racing, where epoxy or phenol resin is still the main 'lattice' of the wonder-composites they use, and where 'loading' with powders like aluminium or bronze is quite a common technique for different applications.
But, point is, a bit of glue and a bit of scrap metal, and you CAN salvage complicated and expensive metal castings, and many other things!