[cricketo]

One of my recent battery builds required some unusual terminals, which I figured I'd make, but I didn't have any copper stock of suitable size... I already had some experience melting things, so it turned out to be a piece of cake... some pictures below. Besides the obvious caveat with machining equipment being expensive, the actual copper element is pretty affordable - electric furnace can be purchased on Ebay for less than $200. I went the lazy route of making a very rough piece of stock with the intention to machine it, but it's possible to cast much nicer bus bars that are ready to use after minimum clean up. Source material for melting was scrap wiring, so definitely decent grade of copper in terms of conductivity.

 

[cricketo]

What did you use for molds?

Just two pieces of angle iron with two spacers in between. Spacers can be any flat stuff like square tubing or flat bar. Between thickness of spacers and the distance between them you can adjust the size of the resulting ingot. But like I said, this method is good enough when the intention is to machine some part out of the resulting metal. For something like bus bars, especially if need many at once, I'd use a more sophisticated mold. For my bus bars I opted just to buy flat stock, cut and drill it - got to pick the battles properly

 

[cricketo]

Making bus bars out of flat stock on a milling machine is probably the easiest thing. Rough cut the pieces, then trim them to length with an end mill. Then drill multiple at once, without even having to measure anything ahead of time.

 

[cricketo]

Those guys have reasonable prices, considering you don't spend any time making that stuff.

I got my flat bar from Amazon, but it was sold by OnlineMetals. I think it was this one : Amazon.com: 110 Copper Rectangular Bar, Unpolished (Mill) Finish, H04 Temper, ASTM B187, 1/8" Thickness, 3/4" Width, 72" Length : Industrial & Scientific
Ended up costing $80 delivered for two 72" pieces. So to compare to above quote, that would be $0.44 plus labor per bar vs $5.8 per bar.

 

[cricketo]

^^ Looks like you paid for, but didn't get, ~3 more pieces with the minimum order adjustment.

Well, I just wanted to see what the service would look like in practice. I think it's decent. There is a weird time/money optimization happening in these projects: on one hand your and my time aren't worth making bus bars by hand, it's better to pay 30-40-50 bucks and have them delivered with laser-cut precision. On the other hand sometimes I can't wait 3-4 business days, and sometimes I am just bored. So I guess in the end it depends...

 

[cricketo]

That and machining copper can be biotch.

That's the common wisdom! But I absolutely had no issues machining my ingots. I used a slitting saw to get the top off, then shell mill to square up the stock, then just a two flute end mill like if going against aluminum. I think a thing to mind is annealed copper, which can feel a lot more soft.