Mini Propane Forge

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Introduction: Mini Propane Forge

In this Instructables, I show how I made my mini propane forge. I know quite a few people have already done this and mine isn't really much different. But I was making my own so thought best film it!

It's very simple starter forge, and ideal for people just getting into knife making or blacksmithing. I have quite a few knife projects planned and needed a decent way to heat the blades up for heat treat.

For this project you will need;

Step 1: Bricks

I used these J23 Soft Fire Bricks. They are nice and easy to work with and light to move around. I needed 5 bricks in total, 4 for the main body of the forge, and 1 for the back to keep the heat in.

Stacked them up in the formation that would give me a small camber in the middle.

Step 2: Cut

The chamber area is quite small as it is. It might be fine if I was working with small bits, but my first knife project is going to be a large chef knife, and this would not fit in. So I measured a 1cm wide groove on the inside of each of the bricks to increase the size.

I used a regular woodworking saw, and carefully cut away the bricks along the lines. The soft fire bricks are super easy to cut through, though they are quite crumbly.

Step 3: Cement

I then took some Refractory Kiln Cement and put it on the bricks. I'm probably going to get ripped apart here, but I just wore some gloves and worked it onto the edges that were going to come into contact with each other. I put it all round and stacked the bricks together and lightly clamped them in place.

I left them to set for 24 hours and it was done.

I'm using a small Propane tank and a torch to heat it. I originally planned to drill a hole to poke the torch in but couldn't decide where I wanted that to go. In the end, I left it just loose at the end and it works just fine.

Step 4: Final Images

And that's it. In the end, I added some pieces of angle iron and welded them together to make it all a little firmer. I think this is totally optional but where I have my forge, I end up having to move it around a lot so I wanted the added security. I will have a few knife projects coming out in the next few weeks. So make sure to subscribe to my Instructables + YouTube Channel.

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    2 Questions

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    i have a place to get firebricks and some Refractory Kiln Cement i am thinking of forge weld heath using a weed torch do you feel these forced can hold up the the heath needed for forge welding a farish rasp

    I don't think the weed torches quite get hot enough. I looked into one but didn't get hot enough for my needs Have a look what the max temp is for the model you are looking at. I might get hot enough just to work the metal? Farriers rasp sounds like a cool project!

    i have a blue torch i have not used it with a firebrick forge , i was thinking a harbier fraight torch for more flame and heat


    • Turbo blast trigger for a burst of extra heat
    • Durable steel nozzle jet and flow valve
    • Insulated ergonomic grip
    • Heats to over 3000º F

    Requires 20 lb. propane tank, not included

    the rasp i want to try to forge weld a hatchet i have seen these on you tube thank,s for that instrucable

    Is one pack (1Kg) of cement sufficient?

    This method is just using already formed bricks rather than having to pour your own cement. Thanks

    18 Comments

    I design and build and run these things.

    .

    1. Combustion is a process. It takes combustible gasses and a fuel. They go in and they come out. You combination of a deep small hole as the single "port" for the process of intake, combustion and exhaust, is a bad idea.

    .

    2. Drill a hole through the back block at about 1/3 of the chambers area, and make it central to the chamber and perhaps pointed down just a little, as hot gas rises up. Watch the natural arc of the flame in open air when horizontal. Hot gas exhausting out the door is only a significant issue on larger burners. Start small on the intake port and if sized correctly for that burner, the effect is to produce a natural slightly carbon rich mixture.

    .

    3. If you do this right, you should get a more or less even "reflective" spread of hot zone, along the ceiling of the furnace. This is fine for a small heating chamber. and it keeps the flame from directly impinging on the steel.

    .

    4. There are two secrets to making a good furnace - one is to watch the gas flow, the turbulence and the mixing and the eddies - and the other is to watch the temperature colour in the different areas. Smooth and Even.

    You should write an Instructable on yours. Since you design and build them it would be helpful to see your design and process.

    Thanks so all this info. Some really great stuff in there. The back brick is just held in place, so I can pull that away if needed. This is just a first forge attempt, I'll make a new better one as needs grow! Thanks for sharing :D

    Point the hole down from inside to outside or outside to inside?

    Nice simple design. With the indirect heat are you able to get the steel hot enough to heat treat or forge? For mine, I have to have the flame directly on the steel to get it hot enough. But my chamber is larger than yours.

    Yeah, that's what I was thinking. Can't get mine hot enough like that either.

    Maybe try adding some more torches to see if it gets hot enough.

    Hi, yes it does. I've done a couple of knives all heat treated perfectly. Using O1. It takes about 10mins maybe to get up to full heat. But definitely gets hot enough. I think Mapp Gas gets hotter? Not sure sorry!

    open at the back?

    No there is a 5th brick at the back. I mention it in the first section. Didn't really show it much though sorry! I left it open on purpose so I can make it bigger if needed!