Charcoal Grill Forge: Become a Blacksmith on the Cheap

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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..

ATTENTION:
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 Comments

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

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!

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.

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.

just make sure its hardwood charcoal otherwise it wont get hot enough.

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?