In this Instructable I show you how to make a high efficiency propane forge. I have made a few forges so I have a good idea how they go together but I will give reference and credit to Ron Reil and his designs, that is where I learned how to build them over 12 years ago.
This forge can be used for knife making, blacksmithing, glass making or anything else you can think of that requires heating up stuff to a really hot temperature.
I have access to a welder so I was able to weld some parts together for this forge but if you don't have access or know how to weld, an option is you can braze the parts together or be creative and bolt things together.
Not included in the steps is how to build an operate a propane burner, I have another Instructable for that, which you can check out here:
Important Warning: Do not attempt this Instructable if you do not have experience with propane and how it burns. If you are not comfortable around propane do not attempt this. When propane if used properly is a very safe fuel but bad things can still happen. This burner is very large and can damage you and property. You have been warned, I take no responsibility if something goes wrong.
Always wear safety equipment when lighting and working on the burner. At a minimum, safety glasses or face shield, cotton long sleeves or leather, do not wear synthetic materials as if they catch on fire they will melt to your body.
Lets get started!
Step 1: Video of the Forge Construction
I highly recommend watching the video for the construction and operation of the forge. The written steps follow.
Step 2: Materials and Tools Used
I bought the kaowool and refractory from http://www.psh.ca the rest I found locally at the hardware store.
A note about ITC-100 refractory used to coat the kaowool, it works by far better than any other cement/mortar like refractory I have used in previous forges. I notice that it heats up quicker and uses less fuel than a previous forge using a regular kiln refractory (don't remember the type). If you have the extra money spend it on the ITC-100.
- Airtank or freon tank or propane tank or steel tube (for the container), at least 10" wide
- Kaowool (ceramic blanket)
- Kaowool board
- ITC-100 refractory or some other type of brush-able refractory.
- High heat stove cement
- High heat BBQ paint
- Steel tube or iron pipe fitting sized for the propane burner
- Piece of 14 gauge or similar thickness sheet steel
- Piece of 1/8" x 3/4" steel flat stock
- Piece of 1" steel square tubing
- 2" x 10-32 bolts
- 3/4" coarse thread screws
Here is a list of the main tools used, some may not be listed.
- Mini-grinder with thin kerf cutting disc
- 10-32 tap
- putty knife
- good quality respirator
- disposable gloves
- welder or propane torch for brazing
- 1" paint brush
A propane burner will be needed to power the forge, see two different designs here:
or see this video for another design
Step 3: The Forge Body
For the forge body is a portable air tank. But you can use anything that is similar, such as a used Freon or propane tank. I have used a steel pipe I found at the scrap yard that worked very well.
The air tank I am using has a built in stand to keep it from falling over so this saves me a step or else I would need to add some feet. I'll leave it to your imagination to add the feet to what ever tank or tube you use, suggestions are some large bolts or weld on some tubing.
I used a pot that was a good size to trace out the size of the opening. A compass could be used as well. I cut the ends off both ends of the tank using a thin kerf cutting disc on a mini grinder.
Step 4: The Burner Mounting Tube
To mount the burner a pipe nipple was tapped and welded to the forge bottom.
The placement of the tube was at the top of the forge and placed on an angle. The hole was marked and then cut out, I didn't have a hole saw the proper size so I drilled holes all the way around the circle and then used a Dremel with a cutting disc to cut it out.
Then the pipe nipple was tapped using a 10-32 thread tap. The bolts will hold the propane burner in place for mounting.
The nipple was then welded to the tank, if you don't have access to a welder, another option is the tube can be brazed to the tank. If you can find a flange for fencing the proper size, it could be bolted to the tank.
Here is an Instructable for building a propane burner or Google Ron Reil propane burner:
Step 5: Forge Floor
The bottom of the forge needs to be lined with fire brick. The firebrick is a durable floor material and can be replaced if you do any amount of forge welding as the flux will eat away at the brick.
The bricks were cut to fit the bottom of the tank and one brick was cut into 1 inch wide pieces as spacers to raise the floor bricks up from the bottom of the tank. See pic.
To cut the brick a wet saw was used, other methods are using a chisel and hammer but the bricked I used were too brittle to cut using that method.
The bricks were placed and then cemented together using high heat stove cement.
Step 6: The Ceramic Blanket and Board
The key material for the forge and insulation is the ceramic blanket and board, it goes by brand names such as Kaowool. The blanket can be purchased in different thicknesses, I recommend getting 1" thick rather than thicker ones as it is easier to work with. For this forge, 2 layers of 1" will be used.
The board is a rigid ceramic board and will be used for the opening and back wall of the forge, thickness is 1".
Important! When working with these ceramic material wear a good quality respiratory and vacuum up any fibers after cutting. You want to keep these fibers out of your lungs!
Step 7: Installing the Ceramic Wool
The circumference of the forge was measured and then the blanket was cut to size. It is better to cut it a bit larger so you can trim it down. To cut the ceramic wool use a sharp utility knife, it is very similar to working with house insulation.
Two layers were installed and the bottom of the fire bricks had some installed between the spacers.
The opening for the propane burner was cut open as well.
Step 8: Back Wall
The back wall is the exhaust port and also can allow for longer pieces of metal to be worked in the forge. It is made from the ceramic board.
To make a template a piece of plastic was draped over the opening and traced out. Then it was transposed to a piece of foam board or cardboard and then traced onto the ceramic board. A utility knife was used to cut the board.
The blanket in the forge compresses so the ceramic back wall was held in place by friction.
Step 9: Front Opening
To keep the inside of forge so it is accessible a removable front opening was installed. On the body of the forge a piece of 1"x1" square tubing had bolt holes tapped so 10-32 bolts would could be installed. Then the square stock was welded to the body of the forge, again brazing could be substituted.
A front "U" bracket was fabricated from a piece of 14 gauge sheet metal, template was free handed, some holes were drilled for attaching the board. A piece of flat steel stock was bent and welded to the "U" bracket.
A piece of ceramic board was cut that was larger than the opening of the forge but the size of the opening is up to you as it needs to be big enough in my case to have tongs fit in and out. It was fastened to the "U" bracket using coarse screws.
The "U" bracket assembly is held in place with by the flat steel stock in the square tubing with the tapped bolts.
Step 10: Refractory Lining
The ceramic blanket and board needs to be stabilized so fibers do not become airborne when the forge is in operation. There are a few choices for the refractory lining, I am using ITC-100 HT which looks like a cement/mortar, however it can with stand extremely high heats. It needs to be mixed with water so it becomes like a slurry that can be applied with a paint brush. The consistency should be like thin pancake batter.
It was slowly brushed onto the inside of the forge and outside, just make sure to cover all exposed ceramic fiber surfaces.
Other refractories can be used and the application will be similar.
Let the refractory dry before operating the forge.
Step 11: Misc Pic
Paint the forge with high heat paint, especially the places where there is exposed metal.
Here are some pics of the forge with measurements included for reference.
Install the propane burner into the forge opening and hold securely in place with the bolts. You want the burner so the nozzle is flush with the inside of the forge wall.
Step 12: Operation of the Forge
Put some safety glasses on and have a fire extinguisher near by. To light the forge, use a long BBQ lighter and put the flame near the burner nozzle inside the forge. Turn on the propane slowly and the forge should ignite. Leave the forge at low power.
Once the refractory is dry, it needs to be cured. Don't operate the forge at full power until the refractory is cured. Run the forge at a lower temperature for 15-20 minutes to let the ceramic fibers and refractory lining "set up".
The forge is ready to be used. Crank up the temperature of the propane burner and observe to make sure everything is working properly.