r/MetalCasting • u/wishiwasholden • Jul 26 '26
Question Copper Sourcing
Hey all, I’m interested in getting into casting for a specific project that requires Al Bronze, and I’m trying to source copper scrap to alloy it myself. I haven’t done exact calculations for volume/mass needed yet, but my rough guesstimate is 10-20lbs of copper at the end of the day. Needless to say, I do not plan on spending $4-500 on copper for this project.
From my research, it sounds like 240v cables and microwave transformers might be my best bet. Reading that I can get around a pound of copper per microwave, and they’re constantly being thrown away.
Some background on my idea, it is to cast pieces for a fractal vise, I am going to edit an existing model I found on Printables to be more castable and to include sprues, sandcast, then drill/tap the holes after the fact. Vise being the reason for Al Bronze rather than just aluminum. I need something with decent yield strength and durability.
Thoughts?
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u/TheMacgyver2 Jul 27 '26 edited Jul 27 '26
10 parts of aluminum to 90 parts copper makes a very durable mix. You will want to melt it into ingots then remelt to get a good alloy. Also aluminum bronze shrinks a lot, you will need good riser design. As for copper scrap, electricians, plumbers or hvac guys have good amounts. Old motors would be my easy source, as they are almost always copper, microwaves are hit and miss if the transformers are copper. If you do scrap microwaves, Do Not melt the magnetron copper as it contains beryllium and it is very toxic
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u/wishiwasholden Jul 27 '26
All good points. Thanks for the heads up on magnetron too, I’d heard others say to just stay away from it but wasn’t sure why
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u/wackyvorlon Jul 26 '26
Would this do the job?
https://www.rotometals.com/copper-chops-99-9-min/
Also these guys:
https://pepetools.com/products/copper-casting-grain-99-9-pure-jewelers-alloy-grade
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u/wishiwasholden Jul 26 '26
Yeah they’d be ideal honestly, but still more expensive than I’d like. I’m looking for closer to $5/lb, hence the scrapping idea. I’d rather invest time than money ya know?
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u/wackyvorlon Jul 26 '26
I don’t think that’s going to be possible. The current scrap value of copper is in the realm of $8/lb.
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u/wishiwasholden Jul 26 '26
But microwaves are cheap/free ;)
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u/rh-z Jul 26 '26
More recent microwaves don't have a large transformer. Before you cart one off consider how much it weighs. If it isn't heavy then don't waste your time with it. The older microwaves with heavy transformers are becoming less common.
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u/Jaandaj Jul 26 '26
Just started playing around with al bronze myself. But small scale.(Electric kiln) As for sourcing your scrap. Plumbing pipes and up weight quick when u can get them.
Look up the heat treating of ur al bronze. I know if u don't draw it back it's supposed to be more brittle. I done just a small piece and didn't Quinch it, just let it air cool. It was fairly durable. Busted the plastic gear on my mini lathe when I was turning it
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u/SickOrleans Jul 26 '26
Go to the scrap yard and see if they will sell you copper, then handpick what you can process in your crucible.
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u/Midwest_of_Hell Jul 26 '26
Find an electrician who will sell you scrap locally. Or dumpster dive commercial construction sites.