Home Made Forge Made From Gas Tank




About: Nothing much about me just that i am young and new at these things

As mentioned in my last instructable Fire extinguishers are amazing and mostly free. What we will be building today is a home made forge capable of melting stainless and we tried glass but it just went mushy.

Shopping list:
Gas tank empty (free)
Gas tank full (have)
Fire extinguishers (free)
Welder (have)

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Step 1: Empty Gas Tank Clean Clean Clean

We attached our gas tank to a BBQ and burned off the last few minutes of gas tank.
Then put a regulator on hung it upside down and turned it on.
Drill small hole in top BE CAREFULL
Drill another hole in bottom

The tank will be quite full with gunk that smells really bad.
To clean it out we then made these holes much bigger then put lots of boiling soapy water washing out threw the gas tank.

Step 2: Building Forge

We marked out a line along the top of the bbq and using saw we put off the top this is going to be our lid that we welded on using a hinge.
This is now our main holder for the forge.

Step 3: Setting Up the Holder

We packed the sides with engineer bricks we are using bottom of fire extinguisher for our melting pot.

Step 4: Flare

What we did here for the flare was put a small 10mil pipe threw to another larger pipe sealing off one end. You will need a 1.5 to 2 hole going wards the front of the top of gas pipe.

The theory is that when you pump gas throw the small pipe and then down into much smaller hole you are injecting quite a large amount of gas to small hole. The hole is back of tube pulls air in mixing with gas.

Step 5: Meliting Stuff

Took around 25 minutes to melt first block of aluminium and then took another 5 minutes per extra bock we added. we have break down of build under images below.

Step 6: Casting

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    16 Discussions


    4 years ago on Introduction

    Where can I find an old fire extinguisher? I want to make this project. I have everything else except the extinguisher.

    1 reply

    5 years ago on Introduction

    You may want to re-title your instructable so that people will be able to find it. What you built is a "foundry furnace", a forge is a little different, it is for heating metal for hot working (i.e. forging). They work a little differently, forges typically aren't any good for foundry work and foundry furnaces are no good for forge work.


    6 years ago on Step 3

    I read this and totally agree with you. You are giving great advice and it is really helpful. Thanks a lot for sharing your thought with us. Keep posting nice information.



    6 years ago on Introduction

    I didn't clean mine before cutting, is that a problem? I mean beyond it really stinking.. I think i've burnt the smell out of it now anyway.


    6 years ago on Step 2

    Thanks for the suggestion. Its really helpful.



    6 years ago on Step 1

    Thanks for the suggestions. Its really helpful for tank clean.

    [url=http://pumpcoseptic.com/]Septic tank pumping and cleaning[/url]


    7 years ago on Step 6

    I think it takes about 4 days to anneal that piece at 973 farenheit. body centered cubic. The next layer sits in the space. One time i melted too much. i tried to pour an aluminum lathe.i have several from ebay. I went to oakland forge. they were making cast iron valves. I went into a building with no sign of melters. I could hear something switch every few minutes. Another building had an arc furnace. One building had an induction furnace. One had a large pot with a heavy lid and gas. I made a heat exchanger which works somewhat. i could not quite melt brass. charcoal will melt small blobs of iron. I will try the next step. Can you guess what it is?

    Good idea using old fire extinguishers for crucibles - I was going to weld mine out of a chunk of old pipe, but your solution sounds more elegant.

    One question:
    If the crucible is a steel fire extinguisher, why doesn't it melt at the same temp as your steel scrap? I see a lot of these setups used for Aluminum melting/casting, but since most people use a steel crucible, they can't melt steel. I'm just curious how you got yours to melt steel.


    7 years ago on Introduction

    Good instructable & good idea.

    I would be very careful cutting on any kind of tanks. You might find a local propane dealer that would either swap a bad tank with you or purge the one you have.

    I have a close friend that was welding on a diesel truck fuel tank that got burned very badly several years ago. Yes, it was filled with water also, vented and cleaned thoroughly prior to welding on it but what I think happened is that the water displaced the fumes and concentrated them into an air pocket. Of course the end result was an explosion and him being physically hurt as well as burned very badly.

    As you seem to be very sharp and you probably though of this, it may help to suggest this to others and / or as a friendly reminder as to what can happen.

    I have a couple of these laying around and I'm going to build one before too long.

    1 reply

    Reply 7 years ago on Introduction

    Yes we mainly just made sure to drill small hole leave for a while then go bit bigger holes. Then wash out then wash out more. Once that was done was happy to cut it open.

    Great please do post up on site.


    7 years ago on Introduction

    Also note, MANY fire extinguishers are made with aluminium shells, not steel like yours.

    Just so people are aware... they may have a puddle of melt in their furnace instead of a crucible full ready to cast... if not careful in selecting material.

    1 reply

    Reply 7 years ago on Introduction

    Good to know all the ones we have opened where steel. Would be nice to have smaller wall on the melting pot.