Making a single-burner propane forge
I have found this small forge to be very handy for setup on a workbench. The body is about 12" in length, which is great for most tool work, knives, and even the majority of work on swords.

To begin with, you will need to have a regulator on your propane tank which can adjust between 5 to 20PSI. A larger range is fine, but most work will only be done in the 5-10PSI range. You will also need the piping to go from your propane tank to the location of the forge. A single 20 pound propane tank can be used for short periods with this burner, but will freeze up after awhile. I suggest at least a 40 pound tank, and I personally use a 100 pound tank. 3/8" copper pipe works well to get the propane to your forge, then use an adapter to drop to the final 1/4" that will feed your burner.


The Burner

The first, and most important thing you will need to make is the burner. The design I used is based on Ron Reil's EZ-Burner, including many of the suggested modifications. The beauty of this design is the sheer simplicity. Not only is the burner itself easy to make, but it does not require a blower fan (like most burners do). Full construction details can be found on Ron's page, but following are the basics...

First off, please note that because I live in Colorado at high altitude, some of my modifications may not work for everyone. That being said, the parts are very cheap, so if something doesn't work right the first time, you're not out much to get a new part and try again.

The main body of the burner is built from standard water pipe parts. You will need a 3/4" threaded pipe, about 8" in length, and a bell which adapts from the 3/4" pipe to a 1-1/2" pipe. In my case, I was only able to locate a 3/4" to 1-1/4" bell, which would have given a restricted airflow. To resolve this, I used a dremmel to grind out the threads on the large end, which not only gives me the full 1-1/2" bore I needed, but also creates a smooth opening which causes less turbulence of the incoming airflow.

The pipe will probably have a rounded lip on the inside of each end. Take a round file and smooth these out, as they will only cause more turbulance in the airflow. Once that is done, you can screw the 8" pipe down to the bell fitting and snug it tightly.

For the jet, you will need to get a 1/8" brass nipple pipe, 2-1/2" or 3" in length, a 1/8" endcap, and a 90° elbow which is threaded for the 1/8" pipe on one end. The other end needs to be threaded for either a 1/4" flare or 1/4" compression fitting. The flare fitting will provide you with a gas-tight seal, but is more difficult to find. Compressions fittings are very common, but do not provide a good seal for propane, thus you will be required to shut off your propane at the tank whenever your forge is not in use. (This also applies to any following instances where I mention using a flare fitting - Compression can be substituted).

To build the jet, screw the brass pieces together. Lay the unit flat across the bench with the elbow sticking straight up. Mark a point exactly in the middle between the inside edges of the elbow and the endcap. You will need to drill a #60 hole at this centerpoint and deburr it as best you can. A bit of steel wool pushed through the pipe can clean out the worst of the shavings.

Now you need to drill a hole in the bell adapter to accept the nipple pipe. For this step, a drill press is highly advised. Use the casting marks on the bell and your drill line to get the holes as near to centerline as possible. The holes should be drilled through the larger side of the bell, and the edge of the hole should come to between 1/8" and 1/4" inch from the edge. The goal here is to have the nipple pipe going across the mouth of the bell, and be as straight and near to centerline as possible. The more accurate you are in this step, the better your burner will function.

Once the main holes are bored, you will need to get some small set-screws and drill/tap one hole from the top of the bell down into the large holes you just drilled.

Put the nipple pipe into the bell and screw the fitting tightly onto both ends. Ideally, you want the 90° elbow to be pointing exactly the same direction as the jet hole. Both should end up pointing straight down the length of the 8" pipe.

Now for alignment. You will need a few feet of 1/4" plastic water line, a 1/4" flare fitting, and a fitting which has 1/4" compression on one end and is threaded for a water faucet on the other end. Use these pieces to put together your test instrument. Hook it up to the water faucet, and turn the water on (just a little). You should have a very fine stream of water now shooting down the length of the 8" water pipe. Move your jet around until you can get the water jet aimed straight down the middle of the pipe, then tighten the set-screws enough to keep the nipple pipe from shifting. Double-check the water stream to make sure the jet didn't shift while tightening the set-screws, then turn off the water and disconnect your test line.

The last piece can also be the most difficult to make. In order for the burner to work at atmospheric pressure, you need a tapered flare on the end of the water pipe. The amount of tapering is very slight - you only change the diameter of the flare by 1/8" for a 1-1/2" length - but the burner will not work properly without it. I started out making flares by hammering a short piece of 1" water pipe. Not only is this tedious work, but it is also not very accruate. My recommendation - buy a pre-made flare which has been machined specifically for this design of burner.

Slip the flare onto the first 1" of the end of the water pipe and tighten the set-screws. Mount the burner in a vice or something which will keep it away from all flamable materials. Attach a regulated propane line to the brass elbow and adjust pressure to about 5PSI. Double-check the area around both ends of the burner! You will have a direct flame of up to 1 foot, and will want to clear away all flamables for several feet. Once you are certain of your work area, turn on the propane while holding a long match or lighter over the flare end of the burner. You should get a flame from the end of the flare, NOT inside the 8" pipe. If you have flame inside the pipe, or the flame goes out when you remove the match, turn off the propane and adjust the flare 1/2" either direction. You will need to adjust this until the flame is self-sustaining. From there, fine-tune the flare until you get the strongest flame from your burner. A dark blue color shows a good adjustment. Lighter blue and cyan coloration shows a flame which is not burning very cleanly. Once you have the flare adjusted to the best point, mark the position of the flare on the side of the 8" pipe. You now have a functional burner!!!


The body of the beast

For the body of the forge, I used a standard 20 pound propane tank, commonly used for BBQ grills. Check with the local propane dealers, you may be able to acquire an old tank which can no longer be recertified. Let them know you intend to cut it up, and they should have no problem letting you take one. I found my tank at a junkyard.

Open up the valve and bleed off as much leftover gas as you can. You will need to have some freinds help you get the valve off once the tank is empty. The valve has a left-handed thread, and will have lock-tight applied, as it's not meant to come off. It took three of us to unscrew the valve from a tank, but you can probably get a propane show to remove the valve for a small fee.

Fill the tank completely with water and let it sit overnight. You are going to be drilling and sawing on the steel, and one spark on a small bubble of propane inside of an enclosed space will make for a very bad day! If you really want to be safe, let it sit for several days and change the water out each day.

Using a hacksaw, you can cut off the top handle and bottom base. The steel will be extremely hard near the weld joints. It doesn't have to be pretty, it just needs to be out of the way.

Now scribe an 8" circle on the top and bottom of the tank. This should be slightly larger than then rings you just cut off. You will want to mark a flat edge about 6" wide across one side of the circle. This flat spot will be where your forge floor sits. It is important to get the flat edge parallel on both sides of the tank so your floor doesn't wobble. I did this with a level and a lot of luck. Do what you can to get it close.

Fill the tank full of water again. The water won't hurt the sawblade, and will prevent unwanted sparks. Drill a large hole inside the top circle. Using a jigsaw with a metal-cutting blade, cut out the top opening (don't forget to leave the flat edge). Pour out the water and cut out the hole from the bottom in the same way. Due to the large opening now present in the top of the tank and the water changes, there should be no further danger of explosions, so you can cut out the bottom without any precautions.

You should now have a shell which is identical on both ends. Use a file to clean up the cut edges and paint the shell with some high-temp paint, like what you use for BBQ grills. For a stand, I used some 3/4" steel bar welded to the shell. Remember to keep the flats of both openings horizontal. At the top-center of the shell, you need to drill a hole large enough for the smaller end of the burner flare to fit snugly in. File this hole to remove sharp edges.

For insulation, you need to locate kaowool, or something similar. You'll want the 8 pound stuff which is denser, and it typically comes in 1" thickness. Wear heavy gloves when working with kaowool, as it is worse than fiberglass as far as getting particles embedded in your hands.

You will need 2 pieces, approximately 12" wide and 36" in length. Roll the first piece inside the shell. make sure it is pushed in tightly and mark the length it needs to be cut at. Add a little to this and cut the kaowool. Push it back into placeand see if you can pack it tightly to allow even the extra length to sit flat inside the shell. More is better, as this insulation is all that is between you and a 2000° furnace. Once you have a good fit for the first layer, repeat and add a second layer of kaowool. The finished insulation should be 2" thick and come right up to the edge of both sides.

Use a gloved finger or large screwdriver to poke a hole through the insultation for the burner flare to fit through. You want to push the insulation back, rather than cutting it out, otherwise this will become a hotspot on your forge. Take the flare off of the burner (you DID mark the position, right?), take out the set-screws, and push the flare through the hole from the inside, so the the larger end is inside the kaowool, and the holes for the set-screws are exposed outside the shell. Position the flare so the bottom end is flush with the surface of the kaowool, which should leave about 1" exposed on the outside of the shell and give you plenty of access to the set-screws. Tack-weld the flare in this position. The flare will last for several years, but will eventually need replaced, so don't weld a full bead all the way around. Place the burner back into the flare at the point you marked and tighten the set-screws.

The finish the body of your forge, you need a floor. I found 1/2" thick ceramic plates at a pottery supply shop. If possible, get a piece which is 6" wide and about 18" in length. Ask if they have any broken pieces they are throwing away, you may be able to get your flooring for free. If you need to, you can cut the ceramic tiles with a metal-cutting blade on a radial-arm saw. This requires lot of work and a lot of patience, but it can be done. The finished piece should sit squarely on the flat sides of the openings. If the flats are not square to each other, your floor will rock slightly. This can be fixed by tucking some extra kaowool under the edges.


The plumbing

The last thing you need are the valves to control the flow of propane to your burner. You will be using 1/4" copper pipe for this, and flare fittings wherever possible, although I have only been able to locate needle valves with compression fittings. You will need two T adapters, a needle valve, and a 1/4-turn ball valve. Bring a line down from the burner to the body of the forge. Put an S-curve in the line to allow some flexability in adjusting the burner's position in the flare. The end of the line will feed into the first T. The second side of the T will feed to the needle valve, and the third side will feed to the ball valve. Take lines from the other side of each valve and feed into the second T. The last fitting on the T will be fed to the main line from your propane tank.

To make the plumbing really solid, I welded a couple of bars across the face of the forge shell, with a bend in them so they are about 1/4" off of the face of the shell. I used automotive hose-clamps to attach the valves and the T's to these bars, then cut the copped pipe to fit. Additionally, I purchased a propane quick-release connector and fitted this to the end of my plumbing. This lets me easily switch the propane line between forges, or get the forge out of the way when I need the workbench space.

DO NOT use standard air-hose connectors or hose for propane!!! The connectors will not seal against propane, and the hose will disintegrate from the inside in about a month. Yes, I tried it. The disintegrating air hose clogged up the burner jets requiring me to make new ones. Propane hoses and fittings are expensive because propane will disintegrate more common materials. Spend the extra for the correct type of lines!

FINALLY IT'S COMPLETE!!! You are now ready to give your new forge a test run. Close the ball valve and the needle valve. Hook up your propane lines and crack open the tank valve. See if you have any leaks around your valves. You should not be able to hear or smell any leaking propane. You can use a rag and soapy water to check for leaks around the connectors. Compression fittings will have slight leaks, but you shouldn't see anything faster than a small bubble every few seconds. With flare fittings, there should be no leakage at all.

To light the forge... I tear off small strips of paper and hold these in a pipe-wrench. Put on your welding gloves, light the paper and hold it under the burner, then crack open the needle valve. The burner should light within a couple seconds, then adjust the needle valve to where the burner will stay lit. After the forge heats up, this can be closed down a little. I generally run at idle with the valve opened about 1/8th of a turn. It doesn't take much. Once the flame is stable, open up the ball-valve. You should have a nice blue flame hitting the center of the forge floor. During use, the needle valve will keep the forge at idle, and the large handle on the ball valve makes it easy to handle with gloved hands. Open it up to heat up your work, then close it down to conserve gas while you are hammering.

Final adjustment of the burner flare should be done once the forge has heated up. Check these images to see what you are attempting to match. Your flame should look like the center image when the ball valve is fully open. When you are running at idle, the flame will generally appear as the bottom image.

If all is working well, you should be able to get a cold railroad spike up to orange heat in just a few short minutes. The main shell should stay relatively cool around the valves - you can still get burned if you lay your hand on it, but an occasional brushing won't hurt. Be wary around the openings as the shell can get red-hot around this area, even with the insulation.

Ceramic tiles are brittle. If this is what you used for the floor, do not simply drop pieces of metal into the forge. You can extend the life of your floor by putting a piece of firebrick underneath it for support.