Dual Fuel Metal Melting Furnace

I got such a great response from the Easy Dual Fuel Furnace Burner that it only made sense to follow it up with the rest of the furnace.

This furnace will be able to handle melting aluminum and bronze with no trouble. In theory it should be able to melt iron too but that's probably pushing it.

I've been using my furnace for a couple years now and it has worked out quite well. My design is based on information I picked up from the backyard metalcasting forum. It's a great resource and community. There are a bunch of furnace builds there exploring a variety of ideas. I recommend checking it out. I'd also read this comprehensive guide for a general overview of metal casting and furnace design.

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Step 1: General Plan

The basic concept is that we are making an insulated container that can withstand temperatures of up to 2600 degrees. The dimensions don't need to be precise but you will have better results if you stick with the general program. I wanted a furnace that would let me cast a decent amount of metal, about 5 lbs aluminum. It needs to be sturdy but as inexpensive as possible to make and run.

The furnace is really simple. It's just a metal container with a lid, a drain and a hole for the burner. It is filled with high temperature insulation to retain the heat and a sturdy inner lining (hot face) to withstand the flame from the burner.

I based my design around a small metal barrel that I got from a salvage place. The sheet metal was thick enough to weld to (pretty much) and not galvanized. The zinc coating on galvanazed metal containers will burn and make a noxious smoke so don't use it. Otherwise any metal container should make a serviceable shell for the furnace. I used bits of pipe and angle iron from my scrap pile for the rest of the metal parts.

I made my own insulation because it was substantially cheaper than buying commercial insulation and I just wanted to try it. I did buy a bag of high temperature refractory cement for the hot face.

The shell is filled with insulation leaving an airspace of roughly 2" on all sides between the crucible and the inside of the furnace.

ivver says: Apr 16, 2013. 8:21 AM

well, I don't know how is in your country, but here by me we sometimes slaughter a pig (to make sausages, bacon and other) so it left behind. I don't know where else would you find hair, try to deal with some local butcher, he could have one. :)

ivver says: Apr 15, 2013. 2:05 PM

You also can get clay stronger with adding some pig hair (belive or not) , I use that method when I need to repair broken clay in furnace. It holds pretty well, try and see at your self. :)

spike3579 (author) in reply to ivverApr 16, 2013. 5:42 AM

Great idea but where does one get pig hair?

x3wayassassin says: Jun 20, 2012. 8:15 PM

instead of using the clay you could also use refractory cement that is rated up to 3000 degrees F

spike3579 (author) in reply to x3wayassassinJun 21, 2012. 5:41 AM

The clay is $12 for a big bag and the refractory cement is $95 for a small bag. I did try it with some left over refractory cement and it just made crumbles rather than holding together. There are other lower temp refractories that would work but they too are awfully expensive.

static says: Jan 5, 2012. 11:10 AM

Great instructable, saved it for future reference. On the 100 W. light bulbs, LOL. I'm certain that 100 W. incandescent bulbs that meet the energy efficiency standards are available

spike3579 (author) in reply to staticJan 7, 2012. 6:37 AM

I don't know....
I think I might start stockpiling a few. Can't get much heat out of a led :P

hag says: Dec 7, 2011. 8:33 PM

I was just wondering what you used for a burner. The only thing that comes to my mind is a propane blow torch, but I doubt that gets hot enough.

spike3579 (author) in reply to hagJan 7, 2012. 6:35 AM

I used this burner. Works great :)

Ace193 says: Jan 1, 2012. 3:46 AM

This is a great 'ible. Your eye for detail in writing this one made it very useful. Keep up the good work!

lewster says: Dec 19, 2011. 11:41 PM

Looks awesome, great 'ible

pj63 says: Dec 2, 2011. 6:34 PM

What a Great Instructable....I've been waiting for a while for this to come up...I have Bricks,Fire Cement and a 25kg bag of Fire Clay to try to build a Smelting/Foundry in my Garden..I needed some final information and your Instr was Brilliant..Thanks and well done very informative...

spike3579 (author) in reply to pj63Dec 3, 2011. 4:25 AM

Sounds like you're ready to go!
PM me or put any questions that come up in the comments
Post some pics of your project.
We want to see....

robotjim says: Dec 1, 2011. 8:25 AM

thanks for the tips, been wanting to try melting
and casting metal for ages...this looks easy enough
I've got no excuse not to !

wasabi237 says: Dec 1, 2011. 8:17 AM

Gold melts at around 1800. Whoo Hoo!

kenwork says: Dec 1, 2011. 7:33 AM

Loved this instructable on creating a metal melting furnace! Thank you!

BTW, your website address is incomplete at the end of the instructable, it is missing the .com.

Here is the complete link for people that want to see Mike and Molly's house :)
http://mikeandmollyshouse.com/

PS118 says: Nov 29, 2011. 3:31 PM

Do you think it would help with the cracking to dry the insulation before pouring the liner?

spike3579 (author) in reply to PS118Nov 30, 2011. 11:22 AM

Probably some. The trouble is that the clay is going to shrink no matter what. The commercial stuff is formulated with parts that expand and contract for a zero net change but it costs more. I don't think a few cracks will really affect the performance of the insulation in this application. You could fill the cracks with mortar if you wanted too.