So I have this idea to build by own metal forging furnace. I am going to dig a square shaped hole in the ground about 3-4 feet deep. I would then bury a 6inch diameter flexible metal tube. One end of the tube would be facing upwards in the hole that I would fill partially up to the rim of the tube. The other end of the tube would be going away from the hole and come up out of the ground a few feet away. This tube hold have a small electric fan blowing air down the tube up into the hole feeding my furnace with fresh oxygen. in the hole I would pile coal or charcoal around the tube. I would line the perimeter of the hole with some bricks to make the burning chamber taller. I would leave a space in the bricks on one side of the hole so I would have a "glory hole" as called in glass blowing to put stuff into the furnace. I would then put a 2 by 2 foot wide, 2 inch thick slab of concrete on top of the bricks to work as a lid. I have everything I need, does anyone have any suggestions/warnings?

Sounds quite interesting. Never really thought of anything like it, makes perfect since though. If you do it soon post a pic or atleast tell us how it went.

I'd be careful with the concrete lid, it'll probably fracture with the heat.

Oh, and to melt metal, you'll need more than a few charcoal briquettes and a small blower (depending on the metal of course). You'd want to look into getting a wood chipper, that way you can make a boatload of small bits and go through them like nobody's business.

Do you mean you'll be using a metal tube inside the burn chamber, or leading up to it, and then the last 6" or so will be a tunnel made from bricks? If it's the former, even if it wont melt, it will oxidize rapidly, and will need to be replaced often.

I'd be careful with the concrete lid, it'll probably fracture with the heat.

Oh, and to melt metal, you'll need more than a few charcoal briquettes and a small blower (depending on the metal of course). You'd want to look into getting a wood chipper, that way you can make a boatload of small bits and go through them like nobody's business.

Do you mean you'll be using a metal tube inside the burn chamber, or leading up to it, and then the last 6" or so will be a tunnel made from bricks? If it's the former, even if it wont melt, it will oxidize rapidly, and will need to be replaced often.Depends what metal. Aluminium is ridiculously easy to melt (in the grand scheme of furnace temps anyway), for example, but for iron you will need something notably more heavyduty/precise then what the OP describes.

To the aforementioned OP:
I would suggest treating all this high temp business with the respect it deserves, ie take every possible safety precaution you can. Protective clothing, a splash screen, decent length tongs, proper cordoning-off of the furnace area, etc. Make sure you have everything ready for whatever youre going to do (molds, perhaps?) before you start to melt stuff. On the one hand if youre going to use bricks youre already dealing with stuff that will degrade after a while anyway, but you may like to look into heat-resistant cement and whatnot. And googling for sites dealing with this kind of stuff is a good idea. Did I mention safety?

Also, why is this in T&T? Sounds more like DIY to me...

For anything concrete that you make, you should mix in sawdust and pumice powder. The pumice helps resist high temperatures and the sawdust will decompose when it gets to temperature, leaving an air pocket which ultimately makes it a better heat insulator and makes it lighter.

Also, you need to let the concrete set and completely dry for at least a week before you put some heat on it, otherwise it could still contain water and would soon crack.

Argon got my tip about sawdust in hah..

most importantly
be careful
if your not and you come back with a metal blob at the end of an arm stump
post pics for laffs

We've built 3 or 4 forges around our farm. 1 was coal/charcoal/whatever, was built on a movable concrete slab, had a huge brake drum for a bowl, some irrigation pipe as a stand/ pipe for the bowl and was powered by a high power squirrel cage fan. You should be able to get all the parts from a junk yard.
My dad built 2 or 3 propane forges out of fire resistant bricks wrapped in steel (he made an octagon by cutting the bricks, then wrapped the outside). We also have a cast iron hand cranked forge that we got at a flea market.

My dad, being a typical DIYer wanted to make firebricks and not buy them. He found a few formulas that were easy to make and easy to find the ingrediants, but he never got them packed tight enough and had to buy factory made bricks.

I wish i had a camera to upload pictures, we have a nice setup.

In my opinion, you want your bowl to be about waist level. Having the forge and anvil at this height just makes the whole process easier.

What you're trying to work with and do is pretty impotant here. Casting? Forging? what metal?

http://www.backyardmetalcasting.com/

^check it out.

^..... beat me to it

I am going to begin with forging steel, I would also like to have enough heat for melting copper and possibly nickel which melts at 2651 degrees fahrenheit, being the highest heat I need. This should be possible because I have learned that even a simple charcoal and brick based furnace can reach 3000 degrees fahrenheit if built properly. I've been thinking I should keep most of the furnace out of the ground because the ground will probably suck out a lot of heat making it hard to reach higher temps. The ground in my area down to about 5 feet is mostly clay making it ideal for my purposes

You're going to need some good charcoal(not briqquettes), the propper design(dome or triangular roof, ect) and the right shit:


http://elliscustomknifeworks.hightemptools.com/firebricks.html

and

http://elliscustomknifeworks.hightemptools.com/castablerefractory.html

So I couldnt find my camera around my house but I will eventually and post pics. I set this thing up yesterday and it worked pretty good, it had good airflow and it reached abou 1000-1500 degrees F. I was able to melt ladles of zinc in only a couple of minutes and was able to melt some aluminum. I want this thing to get hotter so I got more bricks so I could build it bigger and a second fan for more air flow.

http://www.backyardmetalcasting.com/

Man it'd been a couple of years since I visited that site, the last computer I had totally fucking crashed and all of my bookmarks disappeared with it.

Thank you!

Hey i hear fans don't work that well man, if yours is not working well enough instead of another fan, try using a blower off a clothes dryer or a pump from a vacume cleaner.

Also, you probably know this but coal and charcoal are not the same and coal is harder to find and harder to light but it burns longer and i think hotter.

^ coke is better then coal i believe....

A hairdryer works fine. Anything more powerful is overkill and you'll end up with a shitload of ashes and have the stir it the entire time. I usually never used the high setting because I ended up melting some of the blades I was making.

A hairdryer works fine. Anything more powerful is overkill and you'll end up with a shitload of ashes and have the stir it the entire time. I usually never used the high setting because I ended up melting some of the blades I was making.To produce heat you gotta burn fuel (and make ashes), to burn fuel you gotta pump in air, so to produce a lot of heat you gotta pump in a lot of air and burn a lot of fuel.
I wouldn't expect to be able to melt too much iron or copper using just a blowdryer fan.
Vacuume cleaners work great for big, high temp furnaces.

To produce heat you gotta burn fuel (and make ashes), to burn fuel you gotta pump in air, so to produce a lot of heat you gotta pump in a lot of air and burn a lot of fuel.
I wouldn't expect to be able to melt too much iron or copper using just a blowdryer fan.
Vacuume cleaners work great for big, high temp furnaces.

Which is why it's better to use coke. Coke doesn't produce ashes, it just turns into CO and CO2.

Plus, if you used a chimney and a powerful enough fan, the ashes would just blow out of the chimney.

Yea, I wish I was lucky enough to have a cheap source of coal. I was able to get a 5gal bucket full once and had a blast melting shit down with it. Unfortunately there aren't any places in my region that deal with coal so there aren't many sources for it.

A note about blowers;

If you're wanting to use a hairdryer make sure it's not blowing hot air. Cool air = hotter temps. Run it in the cool mode if it has one or clip the nicrome heating elements.

Some shop vacs have both an intake and exhaust port to stick the hose in. It may be possible to put some icewater in the bucket to cool your air down, not sure on that one though.

Coal in this day and age... uffda. I'm fortunate enough that if i ever wanted any, there's a small strip mine not 20 miles from my house and they'd probably love for me to take a 5 gallon bucket and fill up from the belt wastings.

Non-briquette charcoal might be found in a hardware store or something, not 100% on that one. You could make your own if you've got some way to seal a BBQ or other similar container.

I finally got some pictures uploaded here they are:

red hot crucible full of zinc- http://i36.tinypic.com/sdmhx3.jpg
uncovered furnace - http://i38.tinypic.com/28qztb6.jpg
hot furnace - http://i35.tinypic.com/mc9ont.jpg

Awesome!

Is that crucible a piece of pipe with a cap?

sure is. My little brother is going to make me a porcelain crucible in his pottery class and if I ever get serious I will buy a real one offline.

That is the most ghetto assed furnace I've ever seen, pretty sweet. Just curious, can we get a pic of it fueled up, but not burning to get an idea of exactly how it's set up.

look at the uncovered picture of it. The only thing you cant see is that about a foot beneath the bricks with holes the two tubes are sitting on the bottom of the hole to keep them from melting. the bricks with holes are raised up from the tubes/ground on two stacks of bricks.

Damn.
Good job.

Nice dude. You've gotten farther than most people in DIY who talk about metal casting!

Thanks for the advice, but cocain is a bit out of my price range and i think the neighbors might suspect something :D

Nice job hydroponichronic.

Molten metal is not something to be treated lightly, and I've got the scars to prove it, from my high school days.

I think I forgot to address this. The reason coke is better is that it is pure carbon and when it burns it turns into carbon oxides and it leaves no ashes.

That's awesome!