[TowerTalk] Exothermic welding mold

[David Gilbert]

I've never seen any reference to a mold like that, and somewhere I have 
an old  list of all the molds Cadweld made.  If you get desperate, 
though, you could try making your own.

http://www.ab7e.com/exothermic/AB7E_Homebrew_Exothermic_Mold.html

The powder is available on eBay.  The powder comes in pre-measured 
containers depending upon the size of the mold it was intended for, and 
there is always a bit of fine powder at the top for easier ignition.  If 
you lose that fine powder, it can be difficult to fire off the shot 
because it is a reduction (versus oxidation) reaction, but a cheap 4th 
of July sparkler will do the trick quite nicely. The mold I made needed 
about 65 grams of powder so I just bought the 200 gram stuff and divided 
it up into three smaller portions. Worked great.  You'd likely have to 
experiment a bit to determine how much you needed for your mold.

By the way, you'd want a thin aluminum disk to hold the powder in the 
upper chamber before ignition.  I found a bunch of them somewhere, but 
aluminum foil should work just as well.

I once tried to make my own powder since the chemical reaction is pretty 
simple ... just copper oxide and aluminum powder in the right 
proportions.   The problem was that I could only find lab grade stuff as 
a very fine powder, and when I fired it off it all went up just like the 
flash powder they used for taking photographs back in the 1800's.  The 
Cadweld powder is comprised of pretty thick particles to slow the 
reaction and allow the melted copper to flow down into the mold.

Another tip ... the molds work better when they are hot.  Either make a 
couple of test shots first, or GENTLY heat it first with a propane 
torch.  Don't overdo it ... the graphite is just like coal, of course.

73,
Dave   AB7E



On 8/13/2023 7:42 AM, Martin A. Flynn wrote:
> Looking for a mold that can be used to connect three (3) 2/0 
> concentric copper cables to a 3/4 Inch copper clad rod.
>
> Does this exist?
>
> 73 Martin Flynn
>
>
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