Make a Small Blacksmith's Forge




Introduction: Make a Small Blacksmith's Forge

About: I shouldn't have to tell you that using a dagger to undo this little, fiddly screw's a bad idea. AAAAARGH! big project ^^ so practically no chance of instructables from me till july, p'raps? maybe a bit la...

A small forge for Blacksmiths, not a forge for small blacksmiths.
A long-term goal of mine's been to have a forge small enough and well-mannered to keep in my suburban garden, so that means no bituminous coal. I considered a Gas forge but when that turned out to be impractical for the scale of work i want to do, i looked elsewhere. Plus, with a gas forge i'd probably have ended up blowing my legs off.
So, suburban (so no smoke) and i can't use gas.... the only alternative i could see was charcoal. Finding a lost middle-american civilisation in among my socks would be considerably easier than finding the kiind of charcoal i need in the amounts i need. -everyone wanted to sell me a few tons at least-
Eventually, i found something called "smokeless fuel" seemed to be pure carbon or something, so because it was only £1.75 for 10 kilos i decided to give it a try...

Step 1: Find Something to Make the Forge In

I WANTED to use a wheel from a car to do this but i couldn't be bothered going all the way to a place to get it only to carry it home and eventually set it on fire, so i looked closer to home. I ended up using a 12 inch stainless steel cake tin. I never once thought i'd be making a forge in something that vould have been used to hold cakes but it worked really well.
The first thing we need to consider when building a forge is the ariflow. Too much and it gets far too hot. Not enough and it doesn't burn at all. To get the air into the forge, we need a hole through which we can out a pipe. Wheels come with ready-made holes. Cake tins do not. Ergo, i had to make one. "It's only thin steel, what can possibly go wrong?"
I spent something like 40 minutes getting a hole big enough to put the pipe through. SO: this step's instructions: Through Fair means or Foul, Make a hole big enough to fit the pipe through. Make sure the pipe doesn't go too far in or not far enough in. about 1.5 inches was right for me.

Step 2: Add Refractory

"THE FIERCER THE HEAT, THE HARDER IT GETS!" bragged my fire cement. The Refractory reflects the heat back up into the fire, making it more efficient and less likely to melt its way out the bottom of the...cake tin (shudder) It's going to get Seriously hard.
Whatever you do, don't use something that expands too much. Chances are it'll do this at the worst possible moment and carry a cargo of hot coal into your eye. Only use a proper refractory. Mine was rated to 1250 degrees centigrade, lower than I wanted but still plenty high enough. Put about half an inch on the bottom and build it up round the sides leave a working area about 8 to 10 inches wide and 4 deep at least. Make sure that no steel peeks through the refractory.
Allow the refractory to set as per the instructions that should have come with it. Mine needed to be fired immediately after being applied, so no pictures there. Others may need to dry first. Follow the instructions and only fire up the forge when the stuff's ready.
By demand, popular or not, here's some pics on how i added the refractory. I took these the afternoon after i fired it up so the refractory's stained and sootied but i think they get the point across. The refractory should be fairly thin on the bottom, thickish at the bottom of the walls, getting thinner (but not too thin) towards the top. One pic's just the forge itself with nothing added, the other's a pic with the empty refractory pot in for a sense of scale.

Step 3: ON FIRE!

Also known as lighting the forge.
Once you've placed the pipe the correct distance into the forge and applied the refractory, being careful not to obstruct the airflow and to leave a working area big enough for the work you plan to do, it's tome to test-fire it. I suggest doing this at least once before doing any work, just to get a feel for it. I lit mine by putting some wood shavings and paper into it and lighting them, then adding more wood onto that until i was happy that it wouldn't blow out when i turned the blower on (once again, i forgot something important. The blower pushes air through the forge to allow it to reach the correct heat. The blower goes on the end of the pipe that goes into the forge. It needs to be close enough that it doesn't lose too much huff over distance, but far enough away that it doesn't melt with the heat.) Once the blower's on and some more wood's on the fire, put the fuel on, whether you're using coal or charcoal or whatever else. Don't use wood for lots of reasons. It'll take a while for the fuel to take. Put more wood on as needed and put fuel over any gushes of flame coming out (don't panic, the flames from the wood are only 6 inches at the most) Soon enough the wood you used to start the fire'll have burned out and the fuel will be alight. put more on as you need to, but don't put too much on. If it gets higher than the rim of the forge, it's too much. In the picture you can see some bits of wood poking out the sides. The forge itself is on a cinder block (i think i could find a way to get porous cinderblock into ALL my instructables if i tried) Also seen is the hi-tech air blower (old hairdryer) and the space-age way of ensureing that no air is lost in the transition between blower and pipe (sticky tape)


After a while, the forge should be burning well enough for you to start work. The coals in the middle of the fire should be glowing a bright-yellow colour. When you're working with the forge, when you take out the bit of metal you're working on, turn the blower off. The fire won't go out and you'll save some electricity.
When using coal, look out for clinkers, they stick to everything. I'll post more into on this instructable as i get it.

Step 5: LESS FIRE!

To let your forge fire die down simply turn off the air from the blower and leave it. It'll burn down on its own given enough time.
Putting a bucket of water on the forge will be disastrous. You'll get a huge plume of steam laced with incandescant coals, not to mention the fact that you'll give the refractory thermal shock and make it explode. Throwing a bucket of water on it is one of the worst things you can do. Actually, this forge is as safe as a garden barbecueue when handled sensibly but there are serious hazards. Don't let children or animals near it at any times. Don't work if you're preoccupied, drunk or tired.
Read up on the symptoms of carbon monoxide poisoning. If you start to show symptoms, turn it off and get away. NEVER use this in a badly-ventilated area. Always outside.

Step 6: Odd Stuff I Probably Left Out

OK then, don't be stupid, etc.
You'll want to get a poker or something to move the fire about with, i used my tongs. I'll probably have an instructable on making/finding a cheap and effective anvil soon enough.
Have Fun Forging!



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    185 Discussions

    NON-Galvanized black iron pipe would be better for the blower line, the heat can drive off Zinc and very toxic by products of it's combustion. Other than that, excellent work. (If some one else mentioned this, and I didn't spot it, sorry....)

    If you can find someone who works on the railroads, a short section of rail makes a good anvil.

    4 replies

    the local railroad repair station is often wonderfully thrilled to have someone come and remove ties. Just rent a cutting torch and plan to spend the day there. Those 10 foot sections don't load themselves on your truck!

    I have a six inch section that I work my rough forging work with jewelry on. I got it from my father in law who used it as an anvil hard duty for fifty years. I frankly can't see the wear but my wife grew up seeing him whack away on it with his 8 lb sledge as long as she can remember! For fine smooth work, go find 1" steel plate and have them cut you about 6-8" square. If you know someone with a plasma cutter (regular torch will warp your plate) have them blow a hole through it that you can the file to the size you need to insert tools.

    sorry, I said ties, I meant rails! Ties are in too high demand..

    Actually... From experience, cutting or drilling 33lb a foot rail (freight line rail) is not all that difficult. If you took a good reciprocating saw, or large circular saw, with the right blades you could go through it without messing up the rails temper in a few minutes. I drilled 4 holes in the base of my section of rail to secure it to a log with a little water and tungsten carbide drill bit that I got for a couple bucks with Ryobi in about 5 minutes. You just have to do a little research. When cutting steel (or really any metle) the speed and pressure you apply while cutting are almost more important than making sure you have a sharp cutting implement.

    a steel pipe will work quite well, as long as it isn't galvanized. When I built mine, I used a length of exhaust pipe I picked up at the junk yard. The problem with using a galvanized steel pipe is it can let off highly toxic gasses when heated. Basically, you'd just be adding one more thing to worry about with your already dangerous (albeit highly rewarding) new tool.

    how do you turn it off? You can't put water on it. Do you just turn off the blower and wait for it to die out?

    1 reply

    that's a terrific instructibles on the small scale forge..

    And gee! I was right with you until the "don't be drunk or distracted" which I think it's fair to say that being drunk is a nice distraction...(kidding!).

    This is a cheap way for budding jewelers who want to cast, but don't have $2500 for a uber kiln or crucible, to get started..thanks for sharing.

    It's a simple enough design but the stainless steel pot won't last long. Most coffee can forges have much thicker core material made from a mix of paster of paris and silica sand. Also pot like forges like this one are normally made form drum brake rotors which are much thicker tempered carbon steel. I made a couple like this one but with bottoms of small cold water tanks. They work but a thicker metal and more insulation is a priority.

    2 replies

    What could be used is a lining of Kaowool, and cover that with the fire cement. Then the stainless steel can will be fine. Looks like BBQ bricks in the forge, but charcoal would be okay.

    If you put coal in the "modified" design it would still be okay.

    This will last as long, or even longer than a brake drum or water tank forge. This style of design does not depend upon the metal pot withstanding the heat, as in a brake drum forge. In a design such as this, the refractory material is taking the heat, not the metal. The cake tin he is using should not get over a couple of hundred degrees as long as the refractory material was applied properly. Most gas forges work the same way, using a thin steel box and either firebrick or Kaowool for the refractory, yet easily reaching welding temps inside the chamber. This unit, if the refractory is applied properly, should handle the heat from coal with no problem.

    If your cement is on top of your airflow pipe, then how will the pipe even do its job? Someone please respond.

    2 replies

    The cement has to be on top of the airflow pipe, otherwise the intense heat will melt the pipe. However, the front of the pipe should be open to allow airflow into the pot. Basically, you cover the outside of the pipe, but with care not to block the opening.

    If you look closely at the pictures, there is a hole in the refractory cement where the airflow pipe opens into the forge.

    Well, I have to say, I have built one along the same lines. I had nearly zero budget, and it was uglier by far than yours, BUT I could melt 2160 aluminum in it, and nearly steel, and the side was barely hot enough to burn my hand thanks to my super-refractory. That is definitely a "Dont try this at home" maneuver. I nearly fell into it thanks to a piece of rebar on the drive way! Try mixing hardwood ash, plaster of paris, and sand. The ratio was 2/5 ash, 1/5 plaster, 2/5 sand. The refractory is prone to breaking, so dont expect it to be bullet proof, BUT it repairs easy as pie. Just get the "crumbs" get them muddy wet, squeeze out the excess water, and slap on the mud pie as a patch. It can (and should) be fired immediately.

    Remember folks, hot metal and water DO NOT mix. EVER. If you have a setup like this and the fire gets away from you DUMP SAND OR DIRT ON IT. Explosions and flying metal are for wars, not hobbies. Be safe.

    1 reply

    I've used a small unaltered barbeque grill and a coffee can with both the top and bottom cut off and a few holes punched in it as a forge. I use a small clip on house fan in place of a bellows.

    I start by filling the coffee can with charcoal in the grill (I either use purchased briquets or left over charred wood from past BBQs) spray on lighter fluid and get it burning. Once it's going good I insert the iron into the coals (still in the can) and start the fan. I arrange the fan so it's blowing where ever I believe is working best, either blowing through the holes or more often downward into the can. (I usually have the fan clipped to an old folding chair I set up beside the grill).

    When I see the metal is hot enough (by the color) I pull it out and start pounding on it (I'm lucky enough to have an anvil that was passed down through my family.)