How to Build a Propane Forge for Blacksmithing

How To Build A Propane Forge? A Complete Guideline

Propane forge is one of the best tools for your DIYs. You can transform rusty old metals into shiny objects giving new life to your belongings or waste material. It affords you the thrill and skill of creating something useable.

Buying one, however, could take a toll on your pocket.

Why buy one when you can make your own propane forge?

In this informative piece, I will take you through how to build a propane forge and test it.

It’s worth noting that your propane forge doesn’t have to be a complicated one as it can be equipped to work on smaller metal parts. 

If it’s your first time doing forgery, then a smaller propane forge will be a better option because you’re just tinkering with metal pieces.

Here is the step-by-step process of making a ready-to-use propane forge.

Let’s Get Down on How to Build a Propane Forge

First Steps: Gather materials for the propane forge

It’s always important to first gather all the requirements before starting to construct anything. It could help you cut the budget as you may find that some of the needed components are lying idle in your garage or storeroom. Building a propane forge uses locally available parts such as:

Let's Get Down on How to Build a Propane Forge

01. A propane tank for customizing

You can use an old propane tank because most of them feature a five-pointed star type of valve. You may find it in gas refilling stations even though they charge extra for exchanging those old propane tanks.

02. Insulation to contain the heat generated

The propane tank body should be fitted with an insulating layer to hold the heat perfectly well. You may use a firebrick which is cheaper than a high-temperature fiber.

However, this ceramic fiber is quite costly but retains the heat more efficiently than the firebrick.

So you get to choose that which works perfectly for your needs.

03. A metal pipe to direct the propane into the box

This helps to use the propane sparingly without any leakage.

04. Fuel line to connect the forge and the tank

05. A regulator to control the flow of gas

The regulator comes with a pressure gauge to measure the amount of propane going into the forge.

Middle Steps: Build the propane forge

Constructing a propane forge is a simple procedure that involves combining all the parts. However, it may require some vital steps to connect those pieces professionally. Since you have all the building materials at your workstation, it’s time to construct your forge.

Two: Build the propane forge

01. Tools for use in constructing the forge

As discussed earlier, gathering all the needed tools for the entire process makes your work easier. Remember, it’s not just about finding a tool but getting the perfect piece to get your job done.

In this case, a burner and firebrick or ceramic fiber blanketing are the essential components for the task.

You may try to improvise the rest to reduce your budget.

02. Building the forge body

The forge body, in our case, is a portable propane tank. A propane tank comes with a built-in stand that prevents it from rolling while you work. So you won’t need to add some feet to the tank.

Now you need to make a hole in the tank, and you can either use a compass or a good-sized pot to trace out such an opening.

After drawing the part to be removed, you can use a thin kerf-cutting disc fitted on a mini grinder to cut the ends of the tank.

03. Building the forge floor

The forge floor needs to be fitted with fire brick. You can easily replace the firebrick if the brick wears out during welding. Cut the bricks that match the tank’s bottom using a wet saw, as the bricks may be too brittle to cut with a hammer or chisel. Once the bricks are ready, cement them with high-heat stove cement.

04. Fitting materials for insulation

Ceramic board and blanket are the most highly recommended insulation material used in the forge to retain maximum heat. This blanket is available in different thicknesses, but we recommend a 1″ thick one because it’s easier to work with.

The ceramic board is quite rigid with a 1″ thickness, and it’s placed at the back wall and opening of the forge.

05. Setting up the burner

Mounting the burner involves tapping and welding a pipe nipple on the bottom side of the forge. On the other hand, a tube is placed at an angle on the upper side of the forge.

You can mark the holes with a compass and cut the circles using a cutting disc in a Dremel. These holes should be equidistant from each other.

Tap the pipe nipple with a 10 to 32-thread tap while using bolts to keep the propane burner in place during mounting. 

Finally, weld the nipple to the tank or bolt it if you can’t weld it.

Final Steps: Testing the propane forge

01. Acquire and use safety equipment

You need to purchase safety glasses to wear during all the metal works to keep your eyes safe from Sparks or ceramic fibers. Also, put on IR protective glasses when working on large and hot forge.

Three: Testing the propane forge

02. Use soapy water to test for gas leakages at joints

This step will help you to repair any leaking gas lines to prevent damage. If there are leaking joints, they will produce bubbles under pressure.

03. Use a metal file to check if the heat produced is efficient

Acquire a medium-sized file to test how hot the forge gets and how fast it can heat up. If the metal film becomes white and burns completely, then your forge is hot enough.

You can use it for a while to see how long the propane gas lasts. This will help you know how many jobs one propane tank can finish.

04. Set up a location for the forge or acquire a movable forge stand

Mostly, while working with a propane forge, you should place it outdoors for proper ventilation, or it may cause death or property damage.

Therefore, due to this constant movement, your forge requires a work area.

You can create a dolly-style cart floor to hold the propane tank on top and tool storage underneath.

05. Use forge appropriately with specifications of objects to forge, e.g., knife, sword, etc.

Finally, when all the work is done, you coat the exposed metal parts with high-temperature spray paint to prevent rust.

What Does a Gas Forge Consist of?

What Does a Gas Forge Consist of?

Generally, there’s a metal shell that keeps the whole thing from falling apart. There’s a burner or several burners that provide heat. You’ll also need a regulator. And, there’s some kind of insulation; that’s really about it. You crank it up. Flame sheets out of the burner; and it gets hot. It’s just no more complicated than that.

So, let’s start with the overall shape:
First, this isn’t life or death important. There are box-shaped forges, vertical tubes, horizontal tubes, etc. There’s a logic to these things, and they all have some advantages and disadvantages, but that’s not to say that it’s really crazy important which size or shape you choose.

Now, if you do swords, long cylinders are nice. Or, if you do a lot of Damascus, you want to design with an easily replaceable floor because flux will eat it up pretty quickly.

The forge should be big enough:
Forge should be big enough to handle whatever type of knife or tool you typically make. If you look at the top propane forges, you notice they have enough space to do whatever you need to do. And you want it to operate reasonably and efficiently.

So, many things that drive the Forge’s actual shape are driven by whatever little piece of crap metal you’ve harvested to make the shell from.

Old propane tanks are really popular:
If you can weld, making a box shape is relatively simple, so that’s pretty popular too. If I were using a propane cylinder, I’d probably go vertical rather than horizontal. Because you can put fire brick in the bottom and then replace it fairly easily when it gets eaten up by flux. It will happen if you do a lot of Forge welding.

Horizontal cylinders, you basically have to realign totally. It would help if you had ports on both sides of the Forge so that you can stick blades all the way through. If those ports are too small, they’ll choke off your burners and shoot flames way out of the Forge.

If you have no way of tightening up the ports of your Forge, it won’t be super-efficient and will cost more money to operate.

There’s no magic formula here:
If you have a space that’s four to six inches square by 12 inches or so, you’ll be able to make nearly any kind of knife imaginable, even knives a good bit longer than 12 inches.
When you’re forging, you don’t need to heat up the entire knife.

You’re just heating up section by section the chunks that you’re forging. You want enough internal volume so that you’re not sticking your blades right into the bright blue cone of the flame.

Basically two parts to the flame:
They’re basically two parts to the flame, and the inner part has a very oxidizing environment, and you want to avoid it because it caused scaling and decarburization in your blade.

When you’re thinking about a forge, just make sure you properly account for how thick your insulation is. If you start with a 10-inch diameter shell, two layers of ends wall, or
K-wool or whatever will knock you down to about five inches in diameter.

What Type of Forge Should I Make?

Now, let me help you through the decision you might want to make. One general point, there is no perfect forge. Basically, there are three things that you might want to do with a forge.
√ The first is forging itself, 
√ the second is forge welding, and
√ then the third is heat treating.

No Forge is going to do those equally well, especially heat treating. If you really want to specialize in heat treating Forge, it’s just going to be quite different from what you would do to do forging and Forge welding.

So for most of us, the question is, what compromise are we willing to make to get us closest to the things that we really want to do? Therefore, the first question that you need to ask yourself is, What are you planning to use it for?

If you don’t want to make big swords, you shouldn’t make them much longer than 12 inches. Now, if you plan to make Damascus, you will obviously need a Forge that has a big enough bore that you can get the billet into it comfortably.

So personally, I wouldn’t want to go much smaller than 4 inches square internally. Mine’s a little bit bigger than that so that I can comfortably get Damascus billets in before they get all squashed together.

What Kind of Shell Do You Want? 

f you can weld, then you can make a square forward shell of any size you want. You can basically make your own version of the commercial box-type forges like the NC tool knife maker series.

Or you can do it all with big firebrick which will take up more space but should run nice and hot. If you can’t weld or don’t have access to a welder, it’s just a question of laying your hands on the right hunk of metal.

Old propane tanks are very popular. Also, water heater cores big iron pipes, or whatever; in whatever case, you’re talking about a cylinder.

Now, if you want to make swords, I’d recommend making a long horizontal like mine.
Mine’s about 24 inches long, but if you’re not a sword guy, I personally would make a vertical with two layers of refractory walls and ceiling, and then a brick or castable bottom; that way, you can bust it out and replace the floor.


So, I have tried to give you a clear idea about “how a propane forge is made”. And, you know different tasks require different shapes and sizes. It is not that hard to make.

Therefore, if you don’t have enough propane gas experience, don’t attempt to make one. Propane can be very dangerous, so please be very careful regarding safety issues.

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