Gas Forge Build 3: Forge Body


For the forge body I managed to source a 5 gallon air compressor from a garage sale for $10. I took the motor, compressor, gauges and fittings off and put these in my scrap bins. The tank is perfect at 10" in diameter and about 17" long. The mounting plate for the compressor and motor will make a nice base for the forge.
After I ground the pipes and legs off, I marked an opening in one end to cut a 3" x 2" rectangle. I drilled and jig sawed this, although an angle grinder works well too. This will be the back of the forge.
Here I taped around the front seam weld.
I want to be able to open the front completely so I can do maintenance on the interior so I will cut the front off. Cuts nicely with a 3/32" zip disc. I will weld it back on with a hinge and secure it with a couple of brackets and a bolt.
Now I lay out the front opening, taking into account roughly 2" of ceramic blanket and fire bricks in the bottom.
Again I cut this with a jig saw after drilling some 3/8" holes to get the blade started.

 For the burner ports, I am spacing them 6" apart as that's the real spacing on the accelerator system.
With a 1-3/4" hole saw I cut the two port holes.
In the back opening, I added a 3" length of 1" angle iron. This will be a rest for long items that need to pass through the forge.

 The burners need to be supported so these 3" sections of pipe will do the job. Ideally I would have used 1-1/2" schedule 40 pipe, but this schedule 80 was handy.
I drill three holes, an inch from one end at 120° apart. The bit is 13/64".
Now with a 1/4" 20 (National Coarse) tap and some cutting fluid I make the threads.
On the grinder I shape the forge end to approximate the curve of the forge body.  This is the end furthest from the tapped holes.
As a clamp, I use some threaded rod and a giant fender washer. This holds the pipe to the forge body so I can tack weld it on.
Here's the two ports welded on. I am not a stellar welder by any means, but this should hold.
With three 1/4" bolts I test the clamp. This 120° arrangement lets us make small adjustments to centre the burner inside the port.

I've added two 10" extension legs with 1" angle iron. These are simply bolted on to the compressor/motor mounting bracket.

The last thing I need to do is get the black paint off of this thing so I can apply some proper high heat paint.This is called "cooking" the forge. I loaded it up with wood and cooked it for a few hours...out in the yard of course. Marshmallows anyone?

Next we'll put the insulation and refractory cement in the forge.

Something you may want to think about at this stage is if you want to use the forge as a foundry for melting metals. This is one idea I came up with:


Mojo said...

The Convertible is a great idea!

Unknown said...

How far do you set you burner flush with inside of tank or flush inside of insulation and refractory?

D. Comeau said...

The flare tip is just inside the burner opening. Set back about 1/4" so it's not in the way of objects going in and out of the forge. The little bit of opening acts the increase the flare length.

Unknown said...

Looks cool how much did it cost in material to complete ? And where do you get all the wool matting and bricks and such:-)

D. Comeau said...

The forge didn't cost a lot. I got the ceramic blanket for free by simply asking a local refractories supplier if they had any "scraps." The hard bricks are from a fireplace store at a couple bucks each.
The tank was from a broken compressor. The thing that cost the bucks was the pipe fittings, the copper fittings and the MIG contact fitting. All up around $55 out of pocket. The reset was junk yard scrounging.


Unknown said...

Hello, thank you for all the great information on your blog, I found it yesterday and haven't stopped reading since!

I am contemplating this forge build, or just buying a Chile forge and waiting 16 weeks! Anyway, I was wondering if you could share what you used to weld this? I have zero welding experience, and am looking for something pretty basic to accomplish the type of welding you did in this post, as well as tacking damascus billets together someday.

Thank you again!

D. Comeau said...


Thanks for your comments. My welder is a 180 Ampere, but a smaller 140 Ampere model would work fine for these small applications.

Unknown said...

Thank you for your response about the welder. I probably should have been clearer with my original question. What type of welder did you use? MIG, Stick, TIG, etc? Just trying to get a feeling for what is useful/necessary for this type of work. Thanks again!

D. Comeau said...

For convenience I use flux core shielded wire in a wire feed welder.