Improved Gas Burner

For the last few years I've been making knives or casting metal as a hobby. To carry out these tasks, you need a really hot heat source! Making a gas burner is an easy way to heat up metal, and the colour of the flame is a very good indicator of how hot it is. An orange flame isn't hot enough, you need a vibrant Blue flame.

We stand on the shoulders of giants.

I've built a few burners, and my earlier ones were copied off people such as 'The King of Random' and 'The Frosty T Burner'. Their designs are decent and work well, but the air ventilation control is a bit flaky. A little while ago, I was given a proper burner unit that I rejetted for LPG and have been successfully using ever since. The air control is very reliable, and I've been thinking about trying to replicate this design with common parts. You can see the original side by side with my version.

This is the design I came up with. It's easier to make than the original models and, in my opinion, much more reliable, with a robust construction.

I will be using this in an upcoming build, but I wanted to share this with others now.

Lastly, I've only tested this on LPG, not propane, because that's what's readily available here in New Zealand. You will likely need to change the size of the jet nozzle for different gas blends.

1. 150mm by 3/4" threaded pipe
2. 75mm x 3/4 BSP threaded pipe (the entire length needs to be threaded)
3. 100mm by 1/4" BSP threaded pipe (the entire length needs to be threaded)
4. Two 3/4" BSP Female to Female adaptor
5. 3/4" to 1/4" BSP Adaptor
6. 3/4" to 1" Adaptor
7. 1/4" BSP Female end cap
8. 1/4" BSP Female to Female adaptor
9. 1/4" Valve
10. 1/4" Female Hose connector
11. M6 3D printer nozzles
12. Thread seal tape
13. Hose

1. Drill Press
2. Grinder (or hacksaw and file)
3. M6 Tap
4. 1/4" BSP Tap (maybe)
5. 3/4 BSP Tap (maybe)

Please note BSP and NPT are two different types of threaded connections used to join pipes and fittings, with BSP being British Standard Pipe and NPT being National Pipe Thread. The primary difference lies in their thread profiles and how they seal. NPT threads have a 60-degree angle and are tapered, while BSP threads have a 55-degree angle and can be either parallel (BSPP) or tapered (BSPT).

You can jam them together with enough force, but you really need a non-tapered thread for this build.

The 1/4" threaded tube needs to be able to go all the way through the 1/4" to 3/4" adaptor, but the thread normally stops partway through. I flipped this over and placed it into a drill vice, and then carefully drilled through the non-threaded part with an 11.5mm bit. I then flipped it back over and used a 1/4" tap to carry the thread the entire way through.

In hindsight, I could probably have just drilled a larger size hole, but I already had the correct tap.

Carefully mark the centre of the 1/4" end cap and then centre punch it. Drill a small pilot hole and then follow up with the correct size for tapping the thread your nozzle uses.

I drilled a 5mm hole, then tapped this with an M6 thread. From what I've seen most 3D printer nozzles use an M6 thread.

One of my better ideas that I'm quite proud of is using a 3D printer nozzle as the gas jet, they are readily available, made of brass, and best of all, come in a range of sizes. I bought a pack of nozzles and experimented with which size worked best, I've found that a 0.4mm jet works best with LPG. I'm not sure what size will be best for Propane.

First of all test fit the parts to make sure everything connects correctly. Now using good-quality thread seal tape connect the parts together as seen in the photos. Make sure you wrap the tape in the correct direction with the thread (clockwise) so as you screw the parts together it doesn't unwind the tape.

The 1/4" to 3/4 adaptor does not need any thread seal tape as this part does not carry any gas. The adaptor does however, need to be mechanically tightened against the 1/4" female to female connector, which acts as a lock nut.

Since I was trying to reuse as many parts as I already had, I recycled a 3/4" female to female NTP connector. I recommend you make things easier and skip this step by just purchasing a second 3/4" female to female BSP connector. I ended up needing to run a 3/4" BSP tape through the connector so I could assemble the parts.

The breather unit is very important as it allows you to adjust the volume of air that the burner consumes and as such the temperature of the flame.

Clamp the 3/4" threaded tube into place and carefully drill a pilot hole about 25mm to 30mm from one end. Take it slow as the drill bit can bounce around a little as it initially cuts through the thread. Now move up through your drill bits until you get to the final size, I stopped at a 14mm hole.

At this stage the thread will be a little ragged around the hole. Carefully use a small triangle file or thread chasing file to remove all the burrs so the 3/4" female to female adaptor can run freely over the hole. This will allow you to open and close the hole by adjusting the position of the adaptor.

My threaded pipe was 100mm long, and I used an angle grinder to cut it down to 75mm. Once again clean the burrs off with a file or grinder.

Lastly you just need to screw the end with the hole into nozzle unit.

Now you can screw the 1" to 3/4" adaptor onto the 3/4" x 150mm pipe, then screw the other end of the pipe onto the adaptor at the end of the breather pipe.

Following my trend of reusing parts I ground down an old air compressor coupling and screwed it onto the other end of the tap. Once again, you will need to use thread-sealing tape for this.

I pushed on the hose and used my Wire Clamping tool to secure it in place. This works much better than hose clamps as well as looking and feeling great.

This instructional isn't really about how to connect the burner to your gas tank, you can just use a normal connector going straight onto your gas bottle. Do not use a low-pressure BBQ regulator as it will limit the gas flow far to much.

I built a couple of regulator units a while ago, using a standard air compressor regulator, some Nitto air couplers and a gas bottle connector. The Nitto couplers allow you to quickly change between various gas burners.

I've no idea if these components are officially rated for LPG gas, but nothing leaks, and it's been a reliable setup for a few years now.

To light the burner you may need to close the breather hole or cover it with your hand, once the flame is lit slowly open the breather hole by turning the 3/4" female to female adaptor. If you open it too far the flame may go out. The sound and colour of the flame will change as you adjust this; you typically want a blue flame with a fierce sound.

My initial burn was using a 0.3mm nozzle, and if I opened the breather too far, the flame would go out. Swapping to a 0.4mm nozzle seemed to burn much better, and I could open the breather the entire way reliably. It seems I got lucky with a 14mm breather hole and a 0.4mm nozzle with LPG gas.

So far, this seems like a very reliable burner without the weaknesses of the original designs. I hope you find this useful and it allows more people to get into knife making or casting metal.