How to Build a Coal Forge from Scratch

Building a coal forge from scratch is a rewarding project that allows you to create your own tool for blacksmithing, metalworking, or simply for use in heat-based crafts like knife making, jewelry forging, and even farriery. A coal forge is an essential piece of equipment for many metalworkers, as it provides the intense and focused heat necessary to shape metal effectively. In this article, we will go through the process of building a coal forge from the ground up, explaining the materials, steps, and techniques you'll need.

A coal forge operates by creating a controlled fire in a compact, contained space, allowing the user to heat metal to high temperatures in a safe and effective manner. Traditionally, coal was the most commonly used fuel, but modern blacksmiths sometimes use coke (a derivative of coal) for a cleaner, hotter flame. In this guide, we will focus on a coal forge and how to assemble one.

Materials Needed

Before you start building the coal forge, you'll need the following materials:

1. Fireproof Brick (or Refractory Cement)

These bricks are designed to withstand extremely high temperatures and will be used to line the walls and floor of your forge. You can use firebricks, which are readily available at most hardware stores, or refractory cement if you prefer to build a more custom design.

2. Coal or Coke

Coal (or coke, which is a purer form of coal) is the fuel for your forge. Coke burns hotter and cleaner than traditional coal, so it's often preferred by blacksmiths, though both options work for basic forges.

3. Blower or Fan

A blower or a small electric fan is necessary to supply oxygen to the fire. This increases the temperature of the coal and allows the forge to reach high enough temperatures to work with metal. You can repurpose a hair dryer, furnace blower, or even purchase a dedicated forge blower.

4. Steel Pipe or Chimney Pipe

This will serve as the air intake and vent for your forge. A steel pipe will allow you to direct air into the forge and direct smoke or gases away from the work area.

5. Steel Tubing or Angle Iron for Frame

The frame will provide the base structure for your forge. Steel tubing or angle iron is durable and able to withstand high temperatures. It will also support the weight of the forge and keep it stable.

6. Grate (Optional)

A steel grate helps to keep the coal from directly touching the bottom of the forge, allowing airflow beneath the coal bed. This can be useful for even burning and reducing smoke.

7. A Fireproof Base

You need to set your forge on a solid, fire-resistant surface like a concrete slab. Make sure to place the forge in an area that is well-ventilated and away from flammable materials.

8. Tools

Basic tools you will need include a welding machine (if welding parts), a grinder, a hacksaw, measuring tape, and safety gear such as gloves, goggles, and a welding helmet.

Step-by-Step Guide to Building the Forge

Step 1: Design the Forge

The first step is to design your forge. The design will depend on how big or small you want it to be, but generally, the size of the forge will be dictated by the size of the pieces of metal you want to work with. A typical blacksmith's coal forge has the following features:

• Fuel chamber (for the coal or coke)
• Air supply system (to introduce oxygen)
• Chimney or exhaust pipe (for venting smoke)
• Grate or base (for airflow beneath the coal bed)

Sketch out the design on paper or a CAD program if you prefer precision. Make sure to account for adequate ventilation, both to supply air for combustion and to expel smoke.

Step 2: Build the Frame

The frame provides the foundation for the rest of the forge. Begin by cutting the steel tubing or angle iron to the desired dimensions. You'll need to create a rectangular or square frame depending on your design.

• Cut the steel to size: You'll need four pieces for the perimeter and two or more additional pieces for internal support (if necessary).
• Weld the pieces together: If you're using angle iron, you'll weld the corners together to form a rigid frame. If you're using tubing, you can either weld or bolt the pieces together.

Make sure the frame is level and sturdy, as it will bear the weight of the rest of the forge.

Step 3: Construct the Firebox

The firebox is where the coal will burn, and it's crucial that it is properly insulated to maintain high temperatures.

• Lay the fireproof bricks or use refractory cement: If you're using firebricks, lay them in the shape of the firebox inside the frame. Typically, the firebox should be around 18--24 inches deep, 12--18 inches wide, and 12--18 inches high, but you can adjust the dimensions depending on your needs.
• Refractory cement: If you choose to use refractory cement instead of firebrick, you'll want to apply a thick layer to the bottom and sides of the firebox area. Refractory cement will need to cure properly before use, so make sure to follow the manufacturer's instructions for this.

You can also create a grated floor to allow airflow beneath the coal. This can be done by creating a metal grate that sits above the base of the firebox.

Step 4: Install the Blower

The blower is responsible for forcing air into the firebox, increasing the oxygen level and the heat produced. You can use a furnace blower, a hair dryer, or a dedicated forge blower.

• Install the blower at one end of the firebox: This could be done by attaching the blower to a pipe or tube that leads directly into the coal bed. You may need to create a small hole at the side of your forge to accommodate this.
• Seal any gaps: Make sure the blower pipe is securely attached to prevent air from escaping, and seal any other openings around the blower.

The air will be forced through the coal, making the fire burn hotter and ensuring that you can maintain a high temperature in the forge.

Step 5: Create the Chimney or Ventilation

The chimney or ventilation pipe will carry smoke and gases away from your working area. This is especially important if you plan to work indoors or in a small space.

• Install a steel pipe: Attach a steel pipe or chimney to the forge frame, ensuring it is securely fixed.
• Angle the pipe upwards: The pipe should be angled slightly upwards to allow smoke to naturally rise. The longer the chimney, the better the draw (suction) will be.

You may also need a damper or valve to regulate the airflow and control the intensity of the fire.

Step 6: Install the Grate (Optional)

If you're using a grate, place it on the bottom of the firebox. This helps with the even burning of coal by allowing air to circulate beneath the coal bed. You can either create a metal grate or use steel rods that are welded or bolted into place.

Step 7: Final Assembly and Testing

Once the forge is assembled, it's time to test it. Follow these steps to ensure everything is functioning properly:

1. Place coal in the firebox: Light a small amount of coal to test the airflow and heat distribution.
2. Turn on the blower: Observe how the air circulates through the coal. You should see a noticeable increase in the heat as the air flow increases.
3. Check for smoke leakage: Ensure that the chimney is functioning and that no smoke escapes from the sides or bottom of the forge.
4. Test the temperature: After about 10--15 minutes of burning, check the temperature of the coal bed. It should be hot enough to heat metal to forging temperatures (around 1,500--2,000°F, or 815--1,090°C).

Step 8: Safety Considerations

Working with a coal forge can be dangerous, especially if you're handling hot metal or working with fire. Follow these safety guidelines:

• Ventilation: Always work in a well-ventilated area to avoid dangerous carbon monoxide buildup.
• Fire safety: Keep a fire extinguisher or a bucket of sand nearby.
• Protective gear: Always wear gloves, goggles, and a face shield when working with the forge.

Conclusion

Building a coal forge from scratch can be an exciting and fulfilling project, providing you with a custom piece of equipment that will serve you for years to come. The process requires careful planning, attention to detail, and some metalworking skills, but with the right materials and steps, it's a highly rewarding experience.

Whether you're forging knives, tools, or simply experimenting with metal, a homemade coal forge can help you take your blacksmithing skills to the next level. So gather your materials, follow the steps carefully, and get ready to start creating beautiful works of metal art!

View Product