Forge

Kevin Zito

Kevin Zito

KNIFE MAKER
Eventually I’m going to get a HT oven. However, some of things that I’m trying to do require a little heating and bending along the way. At any rate, my question is can I convert this old air compressor into a forge? I’m wondering if it’s too thin. This may be wayyyy too much of a headache especially when forges aren’t that expensive. Please advise and thanks in advance. Z9BFF514C-6BA4-48CB-B903-8C878E682908.jpeg
 
I'm not sure how thick the wall is on an air compressor as I've never cut one open. It's probably not as thick as a propane tank, but I'd bet it's plenty thick enough. I think it just needs to be able to hold its shape (once the ends are cut off) because you'll then line it with Kao-Wool and coat it with refractory material. People make little mini-forges out of coffee cans using the same design. And coffee cans are way thinner wall.

I think that compressor tank does have a nice size / shape for a home forge. Weld some legs on it to put it at the height you want, and then maybe two burners angled to get a good swirl? Looks like a fun project to me!

-andy
 
I have cut up several air compressors. All of them have had pretty thick walls. That being said once it’s insulated you don’t need a thick shell at all. If properly insulated the shell will only get slightly warm. Generally I’m still able to lay my hand on it after forging.
 
Daniel Macina said:
I have cut up several air compressors. All of them have had pretty thick walls. That being said once it’s insulated you don’t need a thick shell at all. If properly insulated the shell will only get slightly warm. Generally I’m still able to lay my hand on it after forging.
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I agree with Daniel it should be plenty thick enough. If it were me I would go with 2” of kaowool or similiar with rigidizer and refractory. If you think you may want to attempt damascus or forge welding one day I would go ahead and plan for at least two burners. If you build them the right way you can run one at a time if you wish. That way you can heat to bend on little gas as possible but if you want you can use both to forge weld or heat bigger pieces.
 
You can use that but I would go with a old Freon tank or bbq tank there perfect size. That tank you have there is to long and will require 2 burners maybe 3. Considering that you can only work about 6inchs of steel in a heat with a hand hammer. I would go with a Freon tank, 1 burner, 2inchs of wool, satanite on top of the wool and itc-100 on top of that. This will make a very efficient forge that will do anything you want in knifemaking. Except giant billets of damascus for that I would recommend a don fogg style forge.
 
I was building one out of a small air tank. I have not finished it for various reasons. Anyway I think that compressor tank would be huge. A freon tank or propane tank would work better. Mine is pretty long with 2 burners 1" of Kao-wool still need to coat with Satinite and ITC. Also put a floor in it made out of a Kiln shelf. I'm hoping to get some time in on it in the next couple months, I just have no time!!
 
Kevin that will work just fine. Pay attention to the OD. The larger the dia the more propane it will need to keep it hot. Will it be a vertical or horizontal forge. Have fun!!
 
Yeah, i don't know how long the tank is but for a single burner forge, I'd cut it down to a maximum of about 16". And I'd put enough fiber blanket in it to get the internal chamber down to a reasonable size. Maybe 6" round inside. And make sure to coat the blanket. If you're planning to go with a venturi burner, make sure the size of the internal chamber isn't larger than what the burner is rated for. I'm personally a fan of forced air burners but venturi can be nice if tuned properly.

I use a small vertical forge for almost all my blade forging since I do most forging on blades by hand, I only heat up 4-5" at a time in it. Then I have a larger horizontal for damascus.
 
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I'm building a two burner forge from an old air tank. For even a two burner you will want to cut the tank back to about 16 -18 inches max. I haven't had a chance to work on it much lately, but I can post some pictures later so you can see what I've done with mine to date.
 
The dia of the tank can easily be changed by slicing out a section lengthwise strapping it closed and welding it together again.
I think some of you may be missing the use of the longer forge to heat treat finished blades which a single burner forge is just not able to do as efficentlly. My three burner unit is way more useful than the single burner I made
 
Von Gruff makes a good point with the heat treating. I try to tell people to design their forge based on what they want to do with it. I certainly wouldn't want to use a long 3 burner forge to forge a 4" hunter. But for heat treating, longer forges are more ideal. I have a heat treat oven so I typically don't use my forge for heat treating.

I am no expert but I do love forging. What I tell people is to think more forges instead of more versatile forges. Basically, you can have 2 or 3 forges that are good at a specific application. Propane is expensive and I try to be as efficient as I can with the process that I'm doing. This is one application where bigger is not always better. You don't want to be heating up a huge chamber to forge a 4" hunter, or at least... I don't want to.

I'm not saying you need to buy 3 forges, but just know what you want to do with this one. Since it's your first one, you may want to make it more versatile. In my opinion, the horizontal forges are more versatile because you typically get a longer heat which is nice for heat treating. I'm not crazy about forging knives in it because it's hard not to heat up the whole thing. So I use a small vertical for that. But I would say that most bladesmiths use a horizontal so it's certainly doable and is what I did for years.
 
Thank you all for the great replies. I’m going to have to research burners. I’m assuming a piece of pipe with a tiny hole drilled in it isn’t gonna cut it.
 
I have posted video of my 3 burner venturi forge holding within those parameters for HT 12C27 (1955F)which makes it a great forge for that and the short 20lb bottle for the singe burner that suits the other applications

As an asside what do you guys pay for your gas. Here the 20lb bottle fill is US$15.50 and I bought a 40b bottle that cost US$29 to fill
 
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