Charcoal Grill Forge: Become a Blacksmith on the Cheap




Introduction: Charcoal Grill Forge: Become a Blacksmith on the Cheap

To me, backsmiths are freakin' badasses. The roar of the fire, and the ping on the hammer striking glowing metal; it's almost mystical. They are legendary figures that have been around since the Romans, manipulating the elements to create long-lasting, useful and desirable stuff. Since the industrial revolution and modern technology, this has become a lost art.

However, this is one hell of a survival skill. I'll show you how to make a forge on the cheap to get started. I encourage you to try it out.

Step 1: Gather Materials

You can get an old charcoal grill just about anywhere. I got one for free through a local classifieds. Wash the grill thoroughly. You won't really need a lid, though once it is built you will want to keep it out of the elements (especially rain).

The only real modification you will make to the grill itself is to construct an air intake, which makes the burn hot enough to soften metal. For this project, you want to use iron (I found this VERY hard to find), or black steel pipe; DO NOT USE GALVANIZED PIPE OR HARDWARE. You can find this at plumbing supply places. This will be one of the pricier areas of the project (still decently priced).

I used all 1" diameter pipe nipples and fittings
- 1 x cap
- 2 x floor flanges
- 1 x T fitting
- 2 x 4" long nipples
- 1 x 6" long nipple
- 1 x 2" long nipple

You'll also need nuts and bolts to connect both flanges to the bottom of the grill simultaneously, a drill, an approx. 5/8" bit, and a 1-1/4" hole saw (maybe).

At the risk of sounding like a broken record, I chose to use stainless steel hardware so it won't give off toxic gas (like zinc coated nuts and bolts might) if it happened to get hot enough. Of course, the nuts and bolts don't match up (bolts sold in even numbers, and nuts in odd numbers) so you'll probably have extra.

Step 2: Assemble Air Intake

Drill a hole in the center of the bottom of the grill (mine already had a hole from the assembly which controlled airflow, which happened to be just about the right size hole).

Assemble all pieces as shown. The piece on the inside is the 2" nipple and one flange.

The bottom nipple with the cap is the 6". The cap at the end of the assembly can be removed to clean out ash that drops down the pipes.

Drill holes in the grill about 5/8" or so, for the bolts. Bolt the two flanges together, sandwiching the grill, so the holes line up, and so the pipes line up with the bottom hole.

Take the assembly and screw it into the bottom flange.

Step 3: Mix and Form Refractory

Refractory is a material which insulates at very high temperatures. This is a must-have for any legit forge.

This step is tricky, because the question is what refractory should be used??? Many people use a homemade mixes from one of the many recipes online, which generally contain Portland cement, fireclay, perlite, and sand. Some mixes can leave you with "clinkers" (glass-like/rock-like areas where the fire was very hot) after burning. In the end, the general consensus was that it would be better to go ahead with a commercial mix specifically made for this purpose, especially since it wasn't too hard to get and about 70 cents/lb.

I spent a lot of time researching this before settling on a lightweight but somewhat weak (not very impact resistant) castable mix from Harbison Walker International that can operate up to 2300 degrees, and has excellent insulating abilities. With the design as it is, most of the refractory surface won't be exposed to temps even close to that. However, I plan to coat most of the surface with some Rutland Furnace Cement from the local Ace or Tractor Supply (resistant up to 2700 degrees) to make it more durable. Note how much weight your grill can reliably hold, as some mixes can be very heavy, and you don't want the forge collapsing while fired up..

One thing to keep in mind is that the commercial mixes are made with crystalline silica, or alumina, which present a hazard to your eyes and lungs, has been linked to cancer (due to inhalation), and can cause silicosis with repeated or prolonged exposure. BE SURE TO USE GOGGLES AND A N95 OR BETTER RESPIRATOR (well fitted). You should work with the dry mix outside or where good ventilation is present, and exposure can be limited for anyone outside. Follow manufacturer mixing, application, and curing instructions. Dispose of according to manufacturer instructions.

Once the water is mixed in, there isn't a danger. I used nitrile gloves when working with the wet mix. Apply the wet mix to the inner bowl of the grill many inches thick. Mine ended up being thickest at the bottom (at least 4in) and thinner around the top (1-2in). The manufacturer recommended NOT troweling the surface as it interferes with drying, so I hand-packed it.

Step 4: Cure Refractory

The manufacturer of the cement I used gave an air-cure time of 24hrs. After that time, light a regular wood fire and let it burn for a half hour then allow to cool completely. Then light again and burn for an hour and allow to cool again. Don't use water to put out fire. The cement has to heat up and cure all the way through. Moisture may weep out the bottom and this is good and normal. Repeat a third time for an hour. Don't heat too much too fast to prevent the moisture in the cement from building pressure and causing eruptions and breaking (explosions?). Again, follow manufacturer instructions.

Once the lining is fully cured and hardened, you're good to go.

Step 5: Fire It Up and Start Working

Now you need something to pump air into the bottom assembly. Many people use old hair dryers, and others have used inflatable mattress pumps. Some people even use shop vacs run in reverse.

I had a mattress pump I hadn't used in a while which worked GREAT; major air flow. In fact, I plan to install a valve where the pump is to be able to control the airflow so it's not running full out all the time and burning out of control.

For fuel, I'm using some regular bituminous coal I got for free on a local classifieds. This will probably piss off my neighbors because of the smoke/smell... This forge is made to withstand high temps of burning coal, so I imagine briquettes or wood charcoal could work too.

Light a regular fire with kindling and small sticks, and start covering with small pieces of coal once it gets going. Pumping some air in at this point will help. I don't know if the ready-light charcoal can be used or what the results might be.

Grab your tongs and metal, and hammer away.



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    23 Discussions

    I like your project! I'd like to reprint this article and photos in Wood-Fired Magazine. Please contact me at

    another option that i used for my japanese style forge as side wall was just nautral clay cat litter it is cheap as hell and it just turns into clay!

    2 replies

    If all you have is "used" cat litter do you remove the "lumps" or do they help the clay stay together?

    I would think the lumps might make it look sort of crappy....

    Several years ago I built a coal forge using an old brake drum. The major portion of a drum is cast iron so there was no refractory needed. For an air source I used the exhaust side of my shop vac controlled by a rheostat. Have since moved (wife's choice not mine) to an area where the coal smoke and smell would get us thrown out so I'm gathering supplies to build a propane forge.

    3 replies

    try charcoal I recommend the one with the cowboy on the bag its not that expensive and tends to be just hard enough to burn for a long time and yet soft enough burn hot enough but do your own tests and the best part it'll smell like a charcoal grill u could also try buying coke from a blacksmithing website or if u can find one a supply shop that will burn hotter than coal and quicker to just a fair warning im currently gathering supplies for a coal/charcoal forge. I've been using a buddies.

    I had thought about charcoal but we are not allowed any type of an outbuilding so everything is in the garage and a small propane forge takes up less space.

    The mattress air pumps are not designed to run continuously. However, they are simple DC motors usually if you have a battery-powered one, you can use a slightly higher power DC-DC regulator to reduce their CFM. If you have an AC powered mattress air pump then they're either the DC motor configuration with some form of conversion from AC-DC, or perhaps they're just direct 110V universal motors. In the case of the latter you can control roughly 60-100% full speed using a triac switching device. The cheapest/fastest/cleanest solution is a "router speed controller" from harbor freight for <$20. This will be more likely to protect your motor than a baffle. At the least, if you use a baffle then make it one that doesn't work exclusively by increasing backpressure (which reduces airflow that cools the mattress pump), but one that redirects some air away from the forge so the pump still runs with minimal restriction and maximum airflow.

    My small comments to an excellent instructable. Thanks for posting!

    I've always been a bit concerned with the idea of building a forge of metal - the very product a forge is built to melt. How does it not melt the forge, if you get the heat high enough to melt metal?

    3 replies

    That is what the refactory is for, it is an insolation layer between the high heat of the forge and the metal structure.

    Thanks, rallekralle & Nathan! I knew it wasn't supposed to melt it to the point of dripping, lol - but that heat level, I always thought would be detrimental to the stability & structure of the forge.

    a forge isn't designed to melt metal, only to heat it until it becomes soft and easy to shape. also the cement is a decent insulator, so the metal part doesn't even get above ~500 °C. so as long as it isn't made of or tin or something, it should be fine.

    If you really need to get started "dirt cheap" then that is a place to save. Literally, DIRT. ANY commercial refractory is going to cost a chunk of change. Dirt is usually free. and high-clay dirt is even better. Just mix it a little moist, so that it clumps, and packs well... then jam it in there.

    1) Yes, it will dry and crack.

    2) No, it is not as good as refractory

    3) Yes, it will work just fine, till you have a chance to upgrade.

    Almost any cracking will be filled with dust from your fuel, and that stuff is a pretty good insulator also. Just remember, "Professional" forges are basically cast iron bowls, so the insulation for your BBQ is only "needed" for high temperature operation (like forge welding, where the insulation concentrates the heat) and to keep the thin steel from oxidizing through (rust or burn, it's just a matter of time and speed).

    For fuel, you can actually get some reasonable work done using hardwood chunks! Hardwood charcoal is better(less smoke and impurities grunging up your steel). BBQ briquettes WILL work, if it is your only fuel, but don't expect forging to be easy or clean. And forge welding is pretty much right out the window.

    As to lighting the fire... I was taught to use the newspaper. Two to three sheets crumpled up, lit on the edge, buried in coal, then turn the blower on. If you have pre-made coke from your last forge session, you can cut that down to a half sheet of newspaper ;-)

    Just remember, the first blacksmiths likely used campfires and rocks to beat metals into compliance. Any more modern technology you use just gives you a head start!

    Video series of taking dirt and firewood, turning more dirt into iron, then forging a weapon of war!

    3 replies

    I run a propane set up now, the first iteration of my forge was literally a pile of bricks with a dirt floor that the burner blew straight on to. After running it for a while I discovered something. In the bottom of the forge, on top of the undisturbed dirt, there was a lump of green-ish glass that I believe once was dirt! If I can get my computer to run i'I'll see if I can find a picture of it.

    The green glass was most likely wood ash. If you heat it to a high enough temperate it fluxes and turns into green glass. I used to do wood fired ceramics and this was actually something we promoted in the kiln.

    Great points, and thank for the addition! to your point, Cobb ovens are dirt cheap and work well, but don't last very long.

    This is fantastic! I've been doing some smithing for a couple of years now, really there is nothing better than hearing snowflakes hissing off of your hot steel in the dead of winter. Anyway, I now run a propane set up, before I had used charcoal. I made it myself thinking that i'd save a lot of time. I did not. It took about 6 hours of constant attention to make about 30 gallons of usable charcoal. Not economically bennificial to me. It did at one point, begin to burn my steel because it was so hot, but I digress. I thought that briquettes would work, just as you said. However they just didn't seem to produce enough heat. They did produce a hell of a lot of sparks though. If I had a source of cheap charcoal that I could consistently get, i'd probably switch back to charcoal.

    theres actually a simple fix to get rid of the galvanizing it just takes a little time and prevent the brown/yellow "smoke causing verry bad hangover": dunk it in water mixed with acid like toilet / draincleaner

    Good warning about using galvanized steel.

    Zinc, which is a coating on galvanized coating, is very toxic if inhaled in dust or fume form. Gas mask and proper ventilation must be in place when you are working on galvanized steel, even if you are just cutting or filing away the steel!

    You really don't want to let others breathe that nasty stuff either!

    You can see if the pipe you got from scrap is a galvanized (zinc-coated) steel by tossing it into a tubful of vinegar or any weak acid. Zinc will dissolve away and you will start to see the vinegar change its color to non-orange tone.

    Or, look for any pseudo-crystalline pattern on the pipe if it has one.

    If you are buying the pipe from a hardware shop, look for DARKER color, preferably with little bit of rust just to be sure (not lots of rust!)

    p.s. Water based filter with weak acid is best for trapping zinc fumes so consider implementing one.

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