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I Forge Iron

New forge need specifics

Paul B

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Okay I have never forged anything. I was a machinery designer for twenty some years and have done a fair amount of machine work. I am a long way from a tool maker. I am getting ready to start to build a coal forge. I did visit one of the members from here and look at a forge he is in the process of building, this helped me with a concept. I am going to build one similar to the one hammer kid shows on this forum. Here are a few basic questions.1) How large should the bottom of the fire box be, length and width? 2) What are the dimensions of the top of the fire box, length and width? 3) What is the angle of the sides of the fire box? 4) What should the depth be of the fire box? This maybe dependent on how big a piece I am going to heat. I'm guessing that the largest thing I will heat til I know what I'm doing maybe something like 1 inch or so square by maybe 8 or 10 inches long.

Any help would be appreciated. I am planning on going to a party put on by the Blacksmith Guild of Central Maryland in a couple weeks, hopefully I will pick up some more tips there as well.


edit: spelling

Edited by Paul B
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COOL! I`ll get u my measurement sthis evning after school!!! But the outer frame is 2 Ft. x 45 inches . I used 1 1/2" x1/8 " angle iron . The firepot is 1/4" mild steel walls and 1/4 " x 1" ban around the top & 1/2" stainless steel for the bottom plate. More info to come.

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2ft x 3ft is a nice size for the hearth. This gives you room to set tools and have a coal supply ready to add as needed. the firepit measurements will depend on the size stock you intend to work but since you are unlikely to be working really big stuff I would recommend a truncated inverted pyramid about 9in square to 3in square. the total depth of your coal fire needs to be approximately 4 inches below your stock and 3-4 inches above your stock. Thus if you build your firepit to be 4 inches deep and flush with the hearth, you will heap your coal 3-4 inches above it.
Then add on the tuyere to that. That is easily done with a pipe tee, (2 or 3 in). Air comes in from the side and ash and clinker pass straight through. Put a grate on top of 2 or 3 pieces of 1/2" rd to hold the coal and a door that will close on the bottom for an ash dump.

I spent about 4 or 5 hrs building my last one to those proportions but not that big. The critical measurements are to have a good coal bed to match your air supply. Most blowers can handle the size above and more. Also have enough coal above and below your work. I have used rivet forges with substantially less coal but couldn't forge weld with out a lot of fussing in one. I also went too big on a firepot and had to blow a lot more air and burn more coal than necessary.

There is a WIDE sweet spot here in which just about anything similar to the above will work. Have a ball.

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I am thinking of a 4" square at the bottom of the fire pot. I am going to use a three inch pipe welded to the bottom. I am figuring 4 - 1/4 inch slots in the 4" square about 2" long for air the air supply. Do you folks think this would be adequate?

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1/4" will work for the air slots, but you may find clinker has a way of obstructing the slots, if you are using coal. I would use anywhere from 3/8" to 1/2" slots, about 3 would be sufficient I would think. The fire will form it's own "cone" of glowing coals, starting in width just past the outside of the slots, and increasingly get bigger as it goes up. Just about all firepots form the fireball differently. If you search the web, you'll find most commercial firepots designed with this in mind. Basically a firepot is a cone/pyramid shape around the outside of the fire burning, allowing you to push coke into the fire as it is formed from all around the fire.

Google "fabricated firepot", you'll find several. I just don't remember where I found them without digging out a binder full of printouts lost somewhere in my house.

You may want to make your tuyere plate removable, so you can change the design until you find what works for you.

Just my .02 Dinar worth, I'm sure someone will correct me if need be.:D

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