Low Cost Foundry/forge





Introduction: Low Cost Foundry/forge

This is my design for a metal melting foundry that also works as a forge.
Materials needed:
1 old beat up standard propane tank
Portland cement
Silica sand
Wood ash
Perlite (not vermiculite)

External parts:
Forge burner
------ I used the burner from this instructable
High pressure gas regulator
Crucible (shown at end)

Tools needed:
Reciprocating saw (for cutting the propane tank)
3" hole saw drill attachment (optional)
1 3/8" hole saw
Small drill bit

Step 1: Prep the Tank

Completely empty the tank of all propane by fully opening the valve. Using your chisel or a hacksaw, slowly cut the brass valve off. Which should expose a roughly 3/8" hole. Fill the tank with water and let it sit for a few minutes then empty it out. Don't throw the valve away because it's solid brass, which you can melt down later!

Step 2: Cut the Propane Tank

First you'll have to cut the top off the tank. Do this first by drilling a small hole in the tank at the desired height, mine being right where it begins to taper in. Then take the chisel and use it to punch a hole big enough for the reciprocating saw blade to fit, and then use the saw for the rest of it.

Step 3: Drill the Large Exhaust Hole.

Using the 3 inch hole saw, cut out the hole right in the top of the tank. My hole saw ended up breaking since it was old and this was the second foundry I've made, so I finished it with the reciprocating saw.

Step 4: (optional But Recommended) Lid Structure Addition

I didn't get a picture of this but basically weld a bunch of random screws onto the inside of the lid to help support the refractory brick.

Step 5: Mix the Refractory and Cast

For the body of the foundry:
Mix 15.6 c Portland cement, 15.6 c perlite, 15.6 c sand, and 15.6 c wood ash. Thoroughly mix and add 33.5 c water. Then add 31.2 c Fireclay and mix until there are no dry pockets. It should be the consistency of very very very soft cookie dough. Pour it into the body of the tank and press a 6 inch diameter by 7 inch high cylinder (basically a large paint can) into the mix until it is right up to the top of the tank.

For the lid:
Mix .8 c Portland cement, .8 c perlite, .8 c sand, and .8 c wood ash. Add 1.25 c water and mix. Add 1.6 c Fireclay and mix. Before you pour the lid, find a 3 inch cylinder to put through the ventilation hole. I used a large spray paint can. Then pour the mix and pack it in, but be careful of the screws welded on!

If you have any leftover cement, make refractory bricks!

Step 6: Drill Gas Supply Hole

Around the center of the tank, drill a 1 3/8" hole through the metal and the concrete. This is to put the burner in.

Step 7: Crucible

You can either buy a ceramic or graphite crucible, which I don't recommend as mine exploded after a while, or you can weld together a metal one which I have now. It's just a 3" ID schedule 40 steel pipe around 5 or 6 inches high. They're based off of the crucibles made on this site: http://backyardmetalcasting.com/crucibles.html

Step 8: Use It!

You can use it to melt anything from aluminum to copper and more as this reaches temperatures of up to 2400°F. You can use it to forge, cast jewelry or other metal parts, and you can melt glass too! Be safe!

PS: if you don't have access to propane as fuel, you can use charcoal with a hair dryer blowing into it instead. It isn't as hot but still works for aluminum and other low melting point metals up to around 1400°F.



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    Great looking work! It is all excellent. I do like the cautions, and of course will heed them.

    BUT, at the risk of seeming ignorant (I'm simply uninformed), I'm in the US, and am not familiar with the abbreviation used in step 5: Step 5: Mix the refractory and cast
    Mix 15.6 c Portland cement, 15.6 c perlite, 15.6 c sand, and 15.6 c wood ash. Thoroughly mix and add 33.5 c water. Then add 31.2 c Fireclay and mix until there are no dry pockets. (and it goes on...)

    What does the lone "c" mean Cubic Centimeters (usually CC)? Cups? (can't be cubits, the project is too small.) ;-)

    Someone please inform me as to the meaning the author is conveying with "c" please. And if you mix too much, what's a safe disposal method for the mix excess?

    I've seen many other projects based on used gas cylinders, and many use "rock wool" or other fireproof fiber insulation, along with firebrick I'm assuming that this insulation goes to higher temps. I only need at most about 2,200° F for forging and later about 425° F for tempering metals in blades, hammers, and tools like chisels.

    Clear up this little confusion for me someone!

    Good instructable! Just FYI, if you want to go to work on the cylinder quicker after emptying it, you can just fill it with water, empty and go to work. You will still smell the odorant, but the flammable vapors will be gone and safe to work with immediately, no need to wait a week. I have welded and cut on a lot of them and that is the procedure I use.

    dry ice works really well at displacing vapor. As it sublimates it goes to the bottom of the tank and forces the residual propane vapor out the top - actually, it displaces everything in the tank. Nothing gets rid of the mercaptain tho except time, sigh.

    Huh that's interesting. I'll have to try that if I make another one

    Something else to try. Before I reseal a tin of oil based paint I flood the inside with propane. Would use butane but it's not something that's readily available. Only place I found that would sell it to me wanted something like $50 a gallon. Anyway, it displaces the air in the tin the same way dry ice displaces anything in a propane cyl. The paint won't form a skin on top - think spray paint.

    I would strongly suggest nitrogen over propane. Nitrogen is non-reactive and will displace oxygen thus protecting your paint. It is also not explosive....

    NOT disputing. N works just fine as well as He, Ar, Kr, Xe or any of the inert gasses BUT you need a dedicated high pressure bottle to contain it and a regulator (who really wants to just crack a valve on 2250 - 3000psi bottle for a tiny amount of content). Just look at all the spray cans you have sitting on the shelf filled with butane, they're explosive as well. What's one more, unpressurized can? Research Propane and you will find it is just about the safest of all reactive gasses. Lookup dust explosions, flour in a drinking straw blown at a candle will explode!

    As a kid and freon was used in cans we used to collect the ones that washed up on the beach and throw (from behind a beached log) them on a beach fire - depending on how full they were there were lots of sparks or no more fire depending on the orientation of the solder seam. Grew up and pursued various careers one of which dealt with plastic explosive, bi-component and other explosive compounds.

    In Russian but idea is clear:


    Well worked out, practical article. Here is video of process:


    That was what I originally wanted to make but it was a little out of my skill set. Induction foundries are pretty cool