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I Forge Iron

Newbie - hello all and gas forge question.


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Firstly Hello to everyone.

Been lurking here for a while and decided to give it a go. Been interested in blacksmithing as long as i can remember but never got around to doing it. Pretty cool stuff you guys have been doing.

Anyways, I plan to build Plan #1 off of this site:

Free Gas Forge Plans

Pretty much exactly like the plans except i am going to go with a cast refractory I think. I may increase the diameter to allow for the thicker walls or perhaps go with the freon bottle idea.

Are there any comments on this design? Has anyone built this type of forge and what was the experience with it?

Also what is the purpose of the concentric rings in the burner?

Please any comments you all have would be most welcome.
Michael Fearn

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Welcome IForgeIron. To answer your question about the concentric rings It is designed as a flame holder. The idea is to slow the air flow at the tip of the burn. This way the flame will stay at the tip of the burner tube, or rather just inside the tip of the burner. But there is a easier way most smiths use what is call a burner flare at the tip of the burner. Flares are just a tapered piece of pipe that does the same thing. The cast refractory will work, but most smiths prefer the blanket material with the paint on coating. The link below will also give you some more ideas on forges and gas burners

Zoeller Forge
Hope this helps

Edited by LarryM
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Welcome to the active branches!

There are quite a number of more developed forge designs but there's nothing fundamentally wrong with that one.

The general dimensions of plan 1, 8" ID x 18" look to be intended for blade making. If blades are what you want to make then this isn't a bad design, except the single burner. This will make the center much hotter than the ends so it'll be tricky getting even heat on a blade for heat treating.

If you were to Put a "T" in the burner tube and make it a two burner design you'd have a much more evenly heated forge and would eliminate the need for the flame holder. The expanded cross section after the "T" will drop the velocity 50% or so and the flame won't blow off the burner outlet.

You don't need a shell made of pipe as in drill pipe, casing, etc. it only has to hold a flame and support a few lbs. of steel. I like SS stove pipe. It comes in lots of convenient sizes with off the shelf fittings like bushings to reduce dia. (makes dandy ends) support brackets for legs, etc.

If you can't find the diameter you want you can snap lengths together at the seam to make what you want. For instance, say you want a 10" ID. with 2" of Kaowool, you aren't going to find 14" dia stove pipe off the shelf anywhere but you sure can snap a piece of 10" together with a piece of 4" and make your dia.

You won't need much for tools either: Tin snips, hand drill, a few bits, a hole saw, pop rivets and some off the shelf hardware.

If you want to cast a hard refractory liner Sonotube (cylindrical cardboard concrete forms available at any builders supply) are perfect. Pick one with an OD the same diameter as the ID of the liner you want, then either position it in the forge shell OR in a Sonotube with an ID the same diameter as the OD of the liner you want to cast.

Once the refractory is set, peel the Sonotube off and let it dry completely before firing.

If you cast a hard refractory liner with the ID you want for your forge but only 1" thick you can wrap it with 1 or better yet 2" of Kaowool. A double lined forge gives you an inner liner that can take a serious beating but has the economy of an insulated forge. It won't heat AS fast as a straight Kaowool lined forge nor be quite as economical but it'll work well. My old forge has a double liner with only 1" of Kaowool and after an hour of forging you can still touch the shell with your bare hand.

There are lots of configurations, liners, burner types, fuels, etc. what you build depends on what you need it to do for you.


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Hi Larry and Frosty, thank you for the information and the welcomes!


I think I understand the principle of the burner flare. It is kind of like a venturi opening and slows down the fuel yes?

Blanket material with a coating it is. I was just thinking of cast refractory because I have used it before to re-brick a boiler, so I am familiar with it. It sounded more durable and I know where to get some. But the quick heat up of the blanket/coating system sounds better. I will look into where to get Kaowool in Vancouver.


Thanks for the tip on the forge plans. There are so many on the Internet, can you tell me if you were me, what plans you would go with? I got most of it figured with the actual forge but the burner design, what design would you suggest?

I chose the blown type because it appeared to me that you could play with the draft settings more than just relying on the venturi effect of the atmospheric burner. Is this an incorrect assumption?

Awesome tip with the SS pipe. I am definitely going to do that!

I would like to make the most versatile forge I can make. Something to knife make, weld, do ornamental work, tools, etc. Something I can learn on for a while. I only have a 60LB anvil (or so, I forget) so I don’t think I will be poking anything too big into it for a while. :)

What sort of burner design/forge size would you guys recommend?

Edited by Egmonster
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Air intake on atmospheric burners (no fan involved) can be controlled with chokes.

If you are totally sold on blown burners, they are great, but more expensive to build. Jymm Hoffman probably has the the simpliest design for them. The major cost is associated with the blower. I think he is recommending a blower from Kayne's and Son that costs about $150 now. Pictures and discussion of his burner design can be found on forgemagic.com in the picture gallery (under Jymm's folder).

An alternative for you to consider is the side-arm atmospheric burner. It is simple to make if you have a few tools. The trickest part is to get the inner burner tip pointing straight down the tube. If you have a lathe, it is a snap... if not, it's a little tricker, but a jig on a drill press will do the job. These burner's can be made very inexpensively. I have seen them sold, complete, for as little as $40. Take a look a the following website for pictures and descriptions of the latest incarnations.

Propane Forge Burner Design / Sidearm Burners

Lots of luck...

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I consider the blown burner *MUCH* more simple that an atmospheric burner as it's really hard to make one that doesn't work and they are very adjustable. Almost any blown burner forge can be tweaked for forge welding. I think the most I have spent for a blower was US$5 for a used one from a HVAC place. No lathe or drillpress needed, no alignment needed!

They are great for a shop forge but for a travelling forge an aspirated burner one wins out as you are not tied to a power source. Though you should not hear my expresions freely vented when the burners have been jostled in travelling and I have to line them up again on-site to get the forge working.

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I make my own naturally aspirated burners and have construction down to 15 mins or so, final tuning can take another 0 - 10 mins. I have a lathe though so that really speeds things up, it'd take me maybe half an hour without it once I got a jig made. Aligning the jet straight down the burner tube is the most critical part of the whole thing.

A gun (blown) burner on the other hand is harder to build but tuning takes only minutes. I can build and tune mine quickly because I've done it quite a few times. Anyway, gun burners work very well with the caveat of needing power available.

There is another very real advantage to a gun burner and that's it's relative insensitivity to back pressure. When you blow air and flamable gas into a chamber to be burned the exhaust MUST have a way to escape. A naturally aspirated burner can only deal with a little back pressure where a gun can deal with quite a bit more.

What you're going to end up with for a forge after learning the craft is not going to be what you started out with unless you are extraordinarily lucky or unimaginative. I used a small pipe forge for years at home as an occasional hobbyist. In the field I built a multitude of field expedient wood fired forges for something to do after the day's drilling was done.

Recently I built a new shop forge that I hope will suit most of my needs from small economical to almost unworkably large. I've uploaded a pic and drawing of the new one and a shot in the door of my old pipe forge right after lighting. There are a couple shots of small scale knife forges, one a single brick forge and one a bean can forge run off an old school gasoline blow torch. All of these forges will weld, my old pipe forge would melt your work if you weren't watching.

There's another style forge I haven't shown but have used often as have many others here and that's a brick pile forge. As the name implies it is simply a stack of fire bricks you can shape to your needs with burners poked in through gaps where needed. I think no matter what a smith has for a regular shop forge there'll always be the need for the occasional weird shaped forge and a pile of firebrick doesn't take up near as much room as several different forges.







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Hmmm. Ok thank you everyone. You have given me much to think about. I think i am going to go with my original blower idea. And build a 2 burner forge out of SS stove pipe. If i make the burner section removable I will be able to transfer it to another forge in the future. I will look into getting Kaowool or a substitute. I will probably end up with a castable layer over the wool.

Sigh. I can't do anything now except plan becasue I am at work for 4 weeks more or so, away from home. Oh well. I can chase down sources and stuff from here anyways.

Thank you everyone!

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