General forge help

[Argetlam]

Hey,
I have an old cast-iron pot, about 1" thick, probably 2' deep and about 1 1/2' in diameter. I want to use this as a small forge ( I'm working towards making a sword and this simply won't do, but I'll deal with that when the time comes ). I need to cut a blower hole in the bottom though. Any suggestions? Also, for something that big (or small, depending on how you look at it), how big of a blower would I need? Will a hand-crank blower work? How big a pipe do I need to move enough air? Any suggestions on attaching said pipe? Any and all help is appreciated.

[ThomasPowers]

You could probably trade the pot for a forge! It's way too deep for what you need. A car brakedrum is a common starter forge pot. To make a deeper fire to get a blade in the neutral or reducing zone you can take a piece of sheetmetal and bend it into a C and place it in the brakedrum and cut a "mousehole" across from the opening of the C that's just above the brakedrum rim. I built one like this once and used it to weld up billets for a couple of years.

Remember when forging a sword you only want the length you can work on before it gets cold to get hot, usually only about 4 inches so you don't need a large forge except for the exception and that's heat treat. But building a forge sized for heat treat which is a rare and short process and then using it for forging which is where 90+ % of the hot work is done is rather a poor idea. Far better to build a forging forge and dig a ground forge for when you need to heat treat something long.

[Frosty]

Find something else, that's WAY too deep to make a usable forge.

It doesn't need to be fancy and certainly not cast iron. A trash can lid will work just dandy if you put an inch of clay in it to keep the galvy from burning off. Or it can be an old BBQ or serving cart or washing machine lid, 55gl drum (Be CAREFUL to know just what was in the drum they can have residue that is toxic, flammable or explosive!!!) even a wooden table will work fine if you put a couple inches of clay on it to keep it from catching fire.

Find an auto repair shop and bum a brake drum or rotor for the fire pot. NOT a semi brake drum, they're too deep. You really only need something 4-5" deep and 5" is deeper than I like for coal but is good for charcoal.

Then using whatever means you have, be it a sabre saw, sharp cold chisel, or whatever, cut a hole large enough to drop the drum in but small enough it will rest on the rim.

Now you have a good sized forge table and fire pot. Pack clay into the table to the top of the brake drum rim. no need to clay the brake drum.

Use whatever is handy for legs, my first one when I was around 10 rested on cinder blocks and was made from a washing machine lid.

Now, plumbing it for the air blast will require a little imagination to connect to the drum/rotor. 2" plumbing pipe is just about perfect, you'll need a "T", two short 2-4" nipples and a longer nipple that will reach to the edge of whatever you use for the forge table. Lastly you'll need a pipe flange or similar to make it up to the drum/rotor.

If you have access to a welder buy a weld flange and you're golden, weld up the lug holes at the same time. If not, you'll need to drill a couple holes in the drum/rotor and using carriage bolts bolt the "Bolt" flange on.

Plugging the lug holes can be something as simple as dropping carriage bolts in them and screwing a nut on from underneath.

Why all the carriage bolts you ask? Because they present less surface to the fire so they'll last longer and being smooth the clinker and your fire tools won't get hung up on them all the time.

Of course you can cover the bolts and lug holes with clay but it isn't necessary unless that's what you need to do.

Now you need is an air grate. Welding a few pieces of rd. bar together parallel with a space between them is popular as is drilling or punching a bunch of holes in a piece of plate steel 1/4" thick minimum. You can use thinner but it will burn out a lot sooner.

Okay, now you have the basic fire pot installed in the forge table and an air grate ready to go. Now for the rest of the tuyere, screw one short nipple into the flange welded or bolted to the bottom of your fire pot. Screw the "T" to this nipple with one arm facing down and the base pointed to the side. (It should look like a "T" laying on it's side) Screw the other short nipple into the arm facing downward and the long nipple into the base facing sideways.

Now you need close the downward facing nipple for an ash dump. A screw on cap works perfectly and is a good option but you'll need to reach under the forge to dump the ash. A somewhat slicker ash dump can be made by attaching an exhaust flapper cap to it and welding screwing, bolting or riveting an extension to the counter weight arm. The long arm will keep it closed and is easy to reach so you can lift it and open the ash dump.

Now for the last part, air. Find a blow drier at Salvation Army another second hand store, garage sale, etc. and make something to hold it in front of the long nipple so it blows into it. I recommend making a cradle affair so you can slide the blow drier into or away from the end of the pipe to regulate the amount of air the fire gets. Believe it or not a blow drier produces plenty of air for a good sized fire. The cradle can be as simple as two pieces of rod or wood even wired or taped to the bottom of the pipe so the blow drier will rest on them.

And that's about it.

Simpler still just dig a hole in the ground about 8" deep and wide by maybe 12" long. Poke a piece of black pipe in through one side about 2" off the bottom and put the blow drier in the other end of the pipe. Outside of using a blow drier for air this is the type forge used to produce some terrificially wonderful forgings for a LONG time.

Frosty

[Argetlam]

Awesome! I'm encouraged. I happen to have a brake drum laying in my yard, I have a welder and I live 10 miles from the nearest Home Depot! And I found an oulet for cheap coal! $20 for a 100 lb. sack! I don't have a blow drier handy but how 'bout a heat gun set on cold? Thank you Thomas, Frosty. I see myself out there working tommorrow if the weather permits!

[Frosty]

A heat gun on cold will work wonderfully. The trick is not making too much blast, not too little. All kinds of things will work but a shop vac or the equivalent has to have a serious air dump or it'll blow the coal right out of your forge.

I'd say you're on the way buddy. Show us pics of what you put together.

You might want to check out the 55 forge in the Blueprints section, it's a fine workng forge anyone who's a little handy can make for next to nothing.

Frosty

[Argetlam]

Made my first knife blank today! I'm not finished with the forge, I just set the drum on some bricks and used a piece of tin with some nail holes in it for a temporary grate type thing in the bottom. I don't currently have any coal but I was able to heat some steel round bar reddish orange with a month old bag of charcoal. I just have to do the final shaping and sharpening on the grinder tommorrow. It's not much, like a glorified butter knife, but you gotta start somewhere, eh? I'm planning on making a table like you said Frosty. I know a dude who can get me a fairly large piece of iron pretty cheap. I'll post pics as soon as I can. Pics of the knife probably tommorrow or Monday. Anyhow, thanks for all the help and suggestions guys. I really appreciate it.

Edited September 20, 2009 by Argetlam