Tips for Building Your Own Blacksmith Forge At Home

CC BY-SA 2.0 Jeff KubinaMany years ago back before the days of the internet I decided to build a forge. It was not a very good forge and probably was dangerous, but nonetheless I built it and fired it and it made some metal glow. At the time I had no idea how to build a forge. I had seen one in action at a festival my family had gone to but that was about the extent of my research. My building skills at the time were probably not bad for my age but I lacked a lot of tools and knowledge that I have now. The internet has also made it a lot easier to research and learn what others have tried and succeeded or failed at.

In today’s age of technology you might be asking why someone would want a forge, a technology that is at least 6,000 years old and possibly much older. If you work with metal as I do for a hobby you probably use equipment such as a welder and plasma cutter. I can tell you that it is very rewarding to take a very hard substance like steel and shape it to your will. I have even used my oxyacetylene torch to make some bends in steel when it was needed but I could only heat a very small area at a time. If you have ever bent steel with a hammer or simply cold formed it with force it can be very difficult if not impossible. The idea that you can heat up metal to the point that it will bend easily and do it with inexpensive equipment you can make is alluring. Bending metal can also eliminate the need for some welds and other work. It is possible to make joints with heated metal by hammering them together. While the forge may be ancient its abilities are still very useful and it can still do things that modern equipment isn’t very good at.

There are many forge designs online but DIYers have two major design choices for fuel: propane and coal. CC-BY-SA 3.0 Eyrian Coal is the more traditional design but propane grants more control. The propane versions tend to be smaller but they are much easier to start stop and adjust. Coal on the other hand has to be ignited and then extinguished when you are done and is messier.

The forge I built as a teen was coal-based although I used charcoal briquettes because that is all I had available. My design was simply a chimney of red bricks stacked about three feet tall with a place to blow air in the bottom. For the air source I borrowed the blower that was for our fireplace insert to circulate hot air. I was able to heat up metal to a glowing orange although I don’t think I ever achieved that desirable almost white hot temperature.

Today I would have used kiln bricks both because they are safer but also because they insulate and hold the heat in better. One of the challenges with building a forge is using something that can withstand the heat and finding a fuel and air source that can generate enough heat. Kiln bricks work well as does some other materials such as koalwool and some cements and products intended to line a furnace. Stainless steel is also a good material to use on the outer part since it can withstand a lot of heat without getting destroyed.

Many DIY designs tend to use steel for the form. Utilizing an old kitchen sink seems to be popular but other designs use large stainless steel pots or old air tanks. The basic coal design simply needs a burning chamber in which the heat can be contained and a source of air blowing up from under the coal. A sink is chosen because it already has a hole in the bottom for the drain that can be used for air. The design simply lines the sink with a heat-resistant material and adds a chimney on top to take the fumes away. One of the larger parts of old forges were the bellows but modern blowers are cheap and easy to get, making that part much simpler. For the blower in a DIY forge many options are available: a leaf blower or even a hair dryer works, or you can use the blower for a fireplace like I did.

Propane forges are a little different in design in that you don’t need a place for the coal to burn and the air doesn’t need to be forced in with a fan. Instead you use a propane burner head that pulls in its own air for combustion and the goal is simply to design a chamber that can hold in and withstand the intense heat. Many design their own burner head as well but it is possible to purchase a propane burner for a reasonable cost. The design of a propane forge tends to be a box or tubular fire box with a hole for the propane burner and an opening to introduce the work piece. As in the coal design it is typically lined with kiln brick or with other heat resistant material. The forge in this case simply retains a lot of the heat from the torch in a confined area.

The forge shape and size may be something you also want to consider depending on your intended use. No matter the heating method there is no predefined shape a forge has to be. If you wanted to use a forge for long things like knives and swords then you would want a forge that was long. If you were making small things like coins or jewelry then you could make a small forge. The larger the forge the more heat you will need. For coal this means more coal and more air, for propane it will likely mean more than one burner.

Both forge designs are straightforward, and the biggest technical challenge in both designs is using materials that can contain the immense heat. The other challenge is safety, as any forge is something you need to be careful with. Building a forge can be a rewarding process, and DIYers can end up with a useful tool to add to the shop.