How to Make a Coal Blacksmith Forge From an Old Propane Grill

Updated on April 11, 2016
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Building a blacksmith forge is fairly easy, and with a few tools and some hard work, you can build your very own pipe tuyere forge very inexpensively. Pictured above is the forge I constructed using a discarded grill, a metal fence post, and a few hand and power tools, and materials available at your local craft or hardware store.


Not sure if you want to go with coal/charcoal or propane? Check out my page on choosing the right fuel for your forge.

Forging on the cheap

I decided to see just how inexpensively I could construct my forge. Because of this, it took a little while longer and a little more work than if I simply threw money at the hobby and bought everything. I did pretty well, and the approximate cost for building the forge was less than 20 bucks. It really CAN be done cheaply.


Pictured on the left is the grill someone decided to get rid of. It was by the side of the road and was in pretty bad shape inside. It also had only one wheel. It happened to be in my neighborhood, so I dragged/rolled it home and began work.

Source

First step: Remove all the plastic

The first step was to remove all the plastic. Plastic has a much lower melting point than metal, and will not withstand even the temperature close to the forge. So remove it now and get it out of the way. Both the left and right shelves needed to be removed as well as the front storage area. Unfortunately, the handle was also plastic and must be removed as well, along with the knobs. You can replace the shelves with sheet metal or some other more durable material for convenience.

Gut the inside

Everything on the inside of the donor grill needs to be removed. These burners were rusty and in bad shape, so they went into the garbage. You should save your grate and cut it apart to practice making things with, once your forge is built. Making "S hooks" are a simple and easy to do starter project

Burner and grate removed.
Burner and grate removed. | Source

Get rid of the big debris

You will need to clean out all the debris and years of burnt on gunk from the grill. It certainly doesn't need to be perfect, you will be burning charcoal in it after all, but it should be passable.

I used a gardening pot lined with a trash bag and placed it beneath the grill. Then I brushed all the debris down the center portion of the grill, down into the pot. This made a significant amount of cleanup much easier.

Muriatic acid at work.  Don't inhale the fumes.
Muriatic acid at work. Don't inhale the fumes.

Clean the forge

This was the most time consuming portion of transforming your grill into a forge. I highly recommend using a pressure washer or sandblaster to clean the grill. I did not have access to either of these tools, but I did have a rough file, and spent about 6 hours working on it over the course of 2 days. Once it was passable, I used muriatic acid to eat away some of the problematic areas, where I could not access with the file.

Muriatic acid is dangerous, so if you go this route, make SURE you use proper protective equipment. Splashes can happen and getting muriatic acid in your eyes could cause blindness. Work in a ventilated area and avoid breathing the fumes.

Good enough

Building the Pipe Tuyere

This is a piece of metal fence post I cut from a portion of my fence I don't use. Attempt to find a metal cap as well. Metal fence posts are galvanized, which means they are covered in zinc, usually to prevent rust. There are a few ways to remove the zinc, which needs to be done before you can use your forge. The easiest way is to soak it in acid, such as the muriatic acid I used earlier. White vinegar will also work, but will need to soak much longer. The final (and easiest way) to get rid of the zinc is to fire up your forge and then go inside, letting the zinc get hot enough to create the fumes and blow away.

Zinc fumes can cause fume fever. The symptoms are usually fever, shakes, weakness, and others. Using black iron piping is much safer, but more expensive.

Older fence posts will have less zinc on the outside, and may even start to rust. This means the coating has gotten thinner, allowing the steel to oxidize(rust), and hopefully will release less gas.


Black steel pipe fittings will last longer and avoid the toxic fume issue.

Use the cap to draw an outline of your cut.
Use the cap to draw an outline of your cut.

Cut holes to fit the pipe.

Cut holes in both sides of your grill in the same place, so that the pipe goes through both sides of the grill. This will allow you to clean your pipe easier by blowing out debris that gets inside without removing the pipe from your forge.

A metal hole saw will be much easier to use than what I did, and have a cleaner cut. Since I did not have access to one, I improvised by drilling many smaller holes and then punching the plate out with a hammer and chisel.

Block holes on the bottom of your forge

Block holes on the bottom of your forge. I cut a piece of scrap metal with a jigsaw, using a wall socket as a template. I drilled two holes on either side of the pieces of metal. I then used the metal to drill holes into the bottom of the grill and screwed them in. Leave one hole, preferably in the center of your forge, unobstructed. You will use this hole to clean the inside of your forge. Place a metal pail of some sort with water under here, to catch anything that might fall during the heating process.


Note: I actually did this out of order and lined my forge before I blocked the holes. Learn from my mistake and block the holes first.

Line the inside of your forge

Insulating the inside of your grill is important for a couple reasons. First, adding insulation will allow your grill to get hotter, bringing it up to the critical temperature faster, thus making it more efficient and allowing you to use less fuel to actually work.

Second, coal can reach very hot temperatures. If your aluminum forge gets too hot, it could actually melt. Aluminum will melt just above 1200 degrees. Coal can get much hotter in the right conditions.

Lining the forge

I decided to line my grill with plaster of paris and perlite. Both can be shipped to your house or bought locally at craft (plaster of paris) and gardening (perlite) stores or a big box hardware store(both).

Mix the plaster of paris according to the instructions, then add perlite. You want to be a little heavy on the perlite. Using your hands is the easiest way to line the grill, but it is very messy. Make sure to work efficiently, the plaster of paris starts to harden fairly quickly. Use a putty knife to press the lining down to make it flatter.

If you have any left over, attempt to cover any holes in your grill that the manufacturer added. Finally, try to build up on either side of your pipe so that fuel will naturally fall towards the pipe instead of next to it.

Drill holes in the pipe

Most pipe tuyere forges have a single line of holes down the length of the pipe, but I wanted a more concentrated flame for smaller projects, so I drilled three lines of holes down a smaller portion of the pipe. If I needed to heat a larger piece of metal, I could drill further down the length of the pipe and place bolts in the holes I wanted to block.

Cap one end of your pipe.

Air for your forge

I used a common blow dryer to force air into my pipe, and it worked quite nicely. More expensive blowers will, of course, be better at forcing air and getting hotter, but the blow dryer did the trick. It lined up nearly perfectly. Later, I might find some sort of coupling to hold the dryer in place instead of me needing to hold it.


Remember, we are doing this on a shoestring budget.

Firing a piece of steel
Firing a piece of steel
A few strikes with a ball-peen hammer on the steel.
A few strikes with a ball-peen hammer on the steel.

Difficulty, total cost of the forge

I attempted to use "grill cleaner" to make it look really nice, but it did not work well at all. Perhaps over cleaner would work better, but it is pretty strong stuff. Honestly, the muriatic acid worked the best.

Building the forge was not difficult, but required some safety equipment and use of power tools. With some care, any handyman or woman could build this without difficulty.

Grill: Found $0

Pipe: On hand $0 or estimate $15 bought

Pipe Cap: $0 or estimate $2 bought

Grill cleaner: $5 (did not work, don't buy)

Muriatic acid: On hand

Plaster of Paris: 7.49

Perlite : 6.49

My cost: 20.30

Potential cost if you need fence post and cap $40-45

How to improve on this build

First, when you cut the holes for your pipe, attempt to place the pipe as low as possible in the grill. This will make it easier to keep the fuel above the pipe, where it can get hotter. This will also require less perlite/plaster of paris mixture to direct the fuel towards the pipe.


Remember to block the holes before you line the forge with the plaster of paris/perlite mixture.

Questions & Answers

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      • profile image

        josh 

        2 months ago

        same

      • profile image

        Doug 

        7 months ago

        Hu and thanks i am going to start my build from your plans today

      • profile image

        wolf48910 

        12 months ago

        the different way to insulate your forge is to use either fire brick or red paver bricks can be picked up at either you local home improvement stores or on craigs list

      • profile image

        Dan 

        14 months ago

        When it starts falling apart how do you recommend patching it up?

      • Devin Gustus profile imageAUTHOR

        Devin Gustus 

        16 months ago from Holiday, FL

        I left the top on, but did not insulate it. I would insulate the top as well next time, to increase heat retention.

      • profile image

        Keir 

        16 months ago

        Hello, Thanks for this!! Im looking to build one this summer, did you insulate the lid to the BBQ? Or do you take the lid off and have an open forge? I've build a smaller one out of a plastic bucket and have a lid to get the temp up...wondering if this same idea would apply?

      • Devin Gustus profile imageAUTHOR

        Devin Gustus 

        3 years ago from Holiday, FL

        Go a little bit lighter on the perlite than what is in my pictures. If the mix in too much then there won't be enough plaster of paris to hold it properly, causing pieces to break off.

        Mix the plaster of paris as directed on the box and then experiment adding the perlite until you get something that you can form onto the sides of your grill.

        Most of the lining is still intact some months later, but be extra careful along the outside edges of the grill. Mine has a few pieces broken off, and they seem mostly near the outside edges. The main issue seems to be from hitting the lining while moving pieces of metal around, so be careful when you are moving things with your tongs.

      • profile image

        Nick 

        3 years ago

        Hello I'm about to use the same mixture to insulate my forge and was wondering if you could tell me how much peri lite to use exactly or at least a better rough estimate and how well this forge has held up for you

      working

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