How to Build a Coal Forge From Scratch

By Simon Graham | Learning and Lessons

How to Build a Coal Forge

Prefabricated or welded forges are great, but not everyone has the time, funds, or skill needed to build a fancy forge. This article will teach you how to build a coal forge using two DIY coal forge plans, where all you really need is a pipe, air supply, and a safe vessel to contain your fire. 

If you are a beginner blacksmith learning how to build a coal forge for the first time, or a seasoned veteran looking for a weekend DIY forging project, these simple methods will get you on your way to metalworking in no time!

Wooden Container Forge

The cheaper and easier homemade coal forge plans are to create your vessel out of wood, stone or brick, and sand. The other materials you will need are:

  • Work Table (standing height)
  • Steel pipe
  • Airflow source
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    Airflow source
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Here is a demo of the process. Read for more detail on how to create your first coal forge:

The most important thing to remember when learning how to build a coal forge is that you need force air supply to push oxygen into your fire. Oxygen is the fuel that makes fires burn hot, and an air supply will increase the temperature of the coal fire enough to melt metal. A good old vacuum that has a blow setting is perfect, but also a hair dryer or any other forge air pump will work as well. All homemade forges require some sort of air supply, so keep that in mind while you are designing yours!

How to Build a Coal Forge - Wooden Container

Set up two saw horses or your work table outside on solid ground. This table provides your sturdy base for the wooden container, so it needs to be able to handle a bit of weight, and of course, a metal-melting pile of coal. You really don’t want that puppy to have any wiggle when you are forging hot metal.

The wooden container should be fairly large, probably at least 2’x3’, and will be built with five sides, leaving the top open. Some boxes can be designed to be disassembled and collapsible, if you are low on space, but a simple yet heavy duty box will do the trick. The joints should be tight enough to not allow sand to pour out as well. Finish off the box by cutting out a circular hole the same diameter of your pipe on one of the short sides.

The steel pipe needs to be cut down to a workable size, which could be about the same length you have made the container. If it is too long air will have a hard time getting to the fire, but too short will bring the fire too close to the wooden box. Feed the pipe half-way into the container through the drilled hole, leaving half the pipe outside of the box. Attached the pipe end that is on the outside of the box to the hose of the vacuum, or whichever air supply you have, using a plank of wood to stabilize and seal with electrical tape.

Find some large rocks that can withstand heat or some bricks, that will be used to stabilize the pipe and create the crude "firepot”. They will also help to create a wall between your fire and the wooden container. Do not use concrete for this, as it has an explosive reaction to excess heat if there is any moisture left in the concrete.

Build a structure around the pipe made of rocks and sand that will keep the pipe completely horizontal. Use a few other rocks or bricks around the container to evenly distribute the weight. Fill the remainder of the box with the sand, leaving a rounded ditch in front of the pipe. Start a kindling fire, turn on the air supply to start blowing in oxygen, and once its hot enough, you are ready to add coal. Before you know it, you have learned how to build a coal forge!

How to Build a Coal Forge

Your simple forge can bring iron to near melting temperatures.

The coal burns very hot when fueled with oxygen. In fact it burns hot enough to turn iron red, just perfect for hammering it into shape.

Metal Container Forge

A more complex, but still simple way to build a DIY coal forge is to use metal as the main container for the fire. Unlike the wooden method, you will not need to use sand or rocks, but you might have to know a little bit of welding to learn how to build a coal forge out of metal. You will also need:

  • Metal Legs or sawhorse
  • Firepot made of heavy duty steel
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    Vertical pipe and ash gate
  • Horizontal pipe for air flow
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    Source of air
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    Electrical tape
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Here is a demo of the process. Read for more detail on how to build a coal forge with a steel container:

How to Build a Coal Forge with Metal Container

Like the wooden model, the metal needs a sturdy way to lift it up to standing height. You can weld on legs or use a sawhorse that is very stable. You can purchase large steel container, don't use galvanized steel, or find a bowl-shaped steel object to cut and weld to your needs.

The firepot needs to be made of heavy-duty steel, as that is where the hottest part of your coal fire will be. It should be as flat as possible to maximize your heat and should allow air flow from your source. You can cover the firepot with a wire mesh to prevent any coal from falling through.

You will also need a vertical pipe to allow ash to fall away, and a horizontal pipe for that all-important air flow. Attach them to the bottom of your firepot. The horizontal pipe should be fitted with an ash gate, which essentially is a flap that holds the air in, but when lowered allows the ash to fall. If you make this have a long heavy tail and attach it with a wire, gravity will hold it in place.

Just like the wooden design, attach the horizontal pipe to the vacuum with a stabilizing wood plank and electrical tape, start the fire, and add the coal. Some parts of this forge will be reusable for a few projects, but the wire mesh might need replacing over time.

No matter how you decide to start on your DIY metalworking projects, now you know how to build a coal forge with cheap and readily available materials!

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