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Hey guys I'm back and I'm wondering how I should build my new coal forge. The one I currently have is a fire extinguisher that I cut in half and attached a shop vac to the bottom. It works but I can only heat blades two to three inches long. So I'm wondering if there's a better way.

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Charcoal or mineral coal? They prefer different setups, but whichever one you use a shop vac is WAY too much air. My Centaur coal firepot is about 8x10 x 4" deep, bottom blown, and can heat about six to eight inches at a time to forging heat, around four inches for welding heat. That's fine, since that's about all you can forge in one heat anyway.

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its mineral coal. (I was lucky to find a deposit in the cliffs near my house!) and the shop vac is a 2.5 hp 1 gallon type with a flow control made from the fire extinguishers leaver. Mine is also bottom blown. I'll post some pics soon.

Edited by AndrewJohnKarow
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Even the little shop vacs are way too much air, which with coal will give a very small very hot fire. And I hope your free coal is good! Not all coal is equal, which is why metallurgical coal sells for nearly $200/ton and bad stove coal sells for around $75/ton. If it's fairly hard and shiny with no yellow or greenish spots or inclusions, and it cokes up rather than just turning to ash, it may be decent.

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then its great coal it doesn't create much ash at all it just burns away

 

Here is a decent video on starting a coal fire:

 

 

Notice how gentle the blast is after it cokes out and is ready for forging.

 

Good coal = cokes well, hot, low ash, low clinker

 

Bad coal = won't coke well, low heat, lots of ash, clinkers that would choke a horse

 

On a 1 to 10 scale, I've used 1 (free from the church basement) to 10 (Blacksmith Depot bituminous).

 

I takes a little experience and experimentation to know the difference.

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