Introduction: Forge

Picture of Forge

In my first instructable I'm going to show you how I made a forge. I hope it gives you some ideas. Please note that this is just one of many ways to do this, and improvisation is the key to making something that you really love.

Step 1: Assemble Your Supplies

Picture of Assemble Your Supplies


- Chopsaw

- Handsaw

- Drill

- Hammer

- Hand plane

- File

- Tape measure

- Pencil

- Buckets for mold

- Bucket for mixing

- Mold for the vent cover


- (1) 4x4x8 post

- (3) 2x4's

- (About 100) 3 inch outdoor nails

- Outdoor wood glue

- 4 cement blocks

- Plaster of paris

- Clean sand

- Cold water

- Blower

- Paracord

Step 2: Cut Your Boards

Picture of Cut Your Boards

I cut four, 2 foot pieces of the 4x4x8 post, and eight, 17 inch pieces of the 2x4's. Save your scrap, because it will come in handy later.

Step 3: Assemble the Stand

Picture of Assemble the Stand

First, I nailed and glued a smaller board on the side of two post pieces,( you will want to pre-drill your pieces, I thought it would be fun to just whack a nail in and I paid for it.) I repeated this, and then joined the two halves together with smaller boards on the side.

Next, I cut notches in four of my smaller boards and nailed them into place. These boards are really crucial weight bearers and it is much better for them to fit tightly than to be lose.

Next, I nailed and glued another ring of smaller boards below the top, spaced a 2x4's width down. This will help keep the legs straight and steady.

Finally, I evened out the wobbly legs by glueing and nailing two thin pieces of 2x4 to the bottom. I used a hand planer to flatten out the slightly un-even top, and I filed down some of the sharp edges so they looked nicer and so they wouldn't snag.

Step 4: Cast Your Forge

Picture of Cast Your Forge

The shape of your forge will be determined by what buckets or other things that you use as a mold. I made mine circular with 2 1/4 inch thick sides and 2 1/2 inch thick bottom. It is 17 inches across,( just because that was the width of the bucket I had laying around), and 12 1/2 inches wide on the inside. The mold for the vent cover I made out of a roll of duct tape and a can lid taped together to make a circular and somewhat thick vent cover.

I poured the plaster, sand, and water, into a bucket and mixed for all I was worth for about three minutes. I used a 1 to 1 to 1 ratio of plaster, sand, and cold water. If I do this again, I will probably use a 1 to 1 to 2/3 ratio. This mix I poured into my mold and it set up surprisingly fast while I held the inner bucket in place. I also filled the mold for the vent cover.

After about one hour I took out the inner bucket and I removed the plaster from the mold for the vent cover. I gave the larger mold about another half hour because I wanted it to harden up a bit more. I was concerned that it might crumble under it's own weight.

After this half hour, I cut away the bucket with my knife. I lifted the forge on top of it's stand to dry faster. I had a feeling that it was still fragile so I was extra careful. I then rounded off the edges and bumps with my file, and cut three blocks with 45 degree angles and glued and nailed them around the forge. I only used three blocks so that I can slide the monstrous forge off, instead of having to lift it off.

Step 5: Add Your Blower

Picture of Add Your Blower

The first thing I did to add an air supply was to pre-drill a hole in the center of the forge. Then I widened the hole with an inch wide paddle bit. Then I used my chisel to make two wide and fairly deep groves in the vent cover. These are so that air can come out from beneath it, while the cover stops charcoal and ash from falling down the blower hole. If/when I use this as a foundry, I will probably take off this cover as it limits air flow.

For the forge's air flow, I chose to install a leaf blower. I had to take the forge off of it's stand and take the stand out of it's cement blocks. I then tied the leaf blower to a main post with paracord with it's nozzle facing close to the hole in the forge. I re-assembled it all, and finally it is done!

I will not run it with full blown heat for several weeks, because it is still slightly soft and it is so thick that I want to be sure that there isn't any water in it so that it won't blow up.


bits_and_bullets29 (author)2017-01-09

could this forge design be used for knife making, like the heat treating process to harden it.

LaraC4 (author)2015-11-09

I made the mini foundry for the king of random. Works excellent. He's also got some other cool diy projects and ideas I've done. But will be making a bigger one to do some metal working other than melting cans into mini muffin pans.

Chief Big Stick (author)LaraC42016-06-30

Be careful with that one. I made the same one and it overheated while I was making a knife turned to powder

JoeyS32 (author)2016-03-21

The firepot is too deep. Also, you will need something for longer pieces of stock to rest on. Heat transfer through the firepot will possible lead to scorching the wood or setting afire.

ahinton3 (author)2015-08-17

How's the plaster/sand mix working out? How durable has it been?

LaraC4 (author)ahinton32015-11-09

I did a smaller version back in the spring with the plaster sand mix. Melted about 100 coke cans. Worked extremely well. Used a empty propane torch bottle for my crucible. Out side of forge didn't heat to bad. But kept it in the metal pail I used as a mold. No cracks or anything so far.

Austin Noble (author)ahinton32015-08-17

Unfortunately, it has been too windy and rainy to fire my forge yet, I'll let you know when I do. It seems to have become harder and stronger just by air drying these few days. As for durability, it has been great (no chipping or cracking). I just keep it covered when it is going to rain.

mixmates (author)2015-08-16

Just out of curiosity couldn't you use an old vacuum motor and secure it permanently rather than propping up the leaf blower (I'd hate melting it). Good work!

xoxo Tactical (author)mixmates2015-08-20

Ive always wondered why no one suggests using one of those Air Mattress Pumps.

LaraC4 (author)xoxo Tactical2015-11-09

I made a smaller version of this with a hair dryer as my blower. Melted cans with. Burned my hair dryer motor up. Lol. Was going to try using a air mattress one next time. And make a bigger forge to work some steel with to make a large blade/knife ect. With.

Austin Noble (author)mixmates2015-08-16

That is a great idea. If I had an old vacuum that I could take apart, I would definitely love to use it and make the blower system a bit more permanent.

you could use an edf turbine for rc jets you can get awesome thrust from a cheap one and have it variable tuned with an esc and servo tester

The first forge I worked with had a vacuum for the blower. Did an excellent job. It was my first experience with metalwork. I see old vacuums set out for trash pickup pretty often, sometimes with nothing actually wrong with them...

Mo Poppins (author)2015-08-26

Really beautiful work! I love seeing a perfectionist's craftsmanship. :) Hope you get a chance to break it in, soon!


leifforrest (author)2015-08-26

I made a backyard forge a long time ago. I used a brake drum from a truck and used standard pipe fittings for air. A 'T' fitting let you clean it out pretty easily. The stand was made out of rebar.
Good job.

jpfalt (author)2015-08-13

You can use chimney flue repair compound in place of the plaster for higher heat resistance. You can also add vermiculite, perlite, granules of charcoal or any other insulating granules that trap air as an insulator to contain the heat and keep the outside of the forge cooler. I have also used 25# per cubic foot insulating bricks for forge bottom and walls the same way. It's also possible to substitute a blow dryer for the leaf blower. In any case your project is really nice work.

irun4fundotca (author)jpfalt2015-08-16

nice looking fordge indeed!

the first mixture of compounds I seen used well was:

perlite, sodium silicate, water, aluminum oxide,

seen here:

jeanniel1 (author)irun4fundotca2015-08-21

This trashcan forge looks like a glory hole we use for working with furnace glass shaping! Is it open on both ends?

sammcleod97 (author)2015-08-17

Hello, I'm learning about forges at the moment and I'm wondering if anybody can help me understand what the point of putting a blower/vacuum to the forge is? Why is it necessary?

tasios (author)sammcleod972015-08-18

A more specific reason is to give the fire more air than it could draw in on its own causing it to burn hotter. Think of it like how you blow on a small camp fire when it starts to cause it to grow (because it's getting more air and burning hotter).

stoobers (author)sammcleod972015-08-17

You need to run the forge with an air blast to get the temperature up high enough to heat steel until the steel glows. When the blast is on, the fire will make a howling sound and burn purple-ish (if you are burning coal.)

sammcleod97 (author)stoobers2015-08-17

Thanks for the help!

liderbug (author)2015-08-17

Nice for long term work. Years back I needed to make "a" chisel. Mothers Kerby (set to blow), broke the bottom off of a pop bottle (insert hose), coffee can buried in the ground, bottle top stuck in can bottom at an angle. Paper+kindling+match - power for 1 sec., ... 2 sec.,... coal, ... 3 sec... coal,... 10 seconds... on. When done the vac went back in house the rest in the trash.

primosanch (author)2015-08-16

Looks very nice. Thanks for sharing.

Oldbear (author)2015-08-16

The bottom T also helps with any rain/moisture that might otherwise run into your blower. Nice instructable. I will be using your ideas in my own forge.

Austin Noble (author)Oldbear2015-08-16

Thanks! I'm glad it helped you.

moonsoup (author)2015-08-16

Actually, Depending on the humidity of where you live you might want to dry it with low heat for a while to drive all the moisture out ...every time you use it... in some places your plaster will build up moisture just from sitting around. That's why ...kiln bricks and refractory block.

DAYJAY (author)2015-08-16

Beautiful casting job. Please post results of first firing.

jbrauer (author)2015-08-14

I second the vote for a cleanout on your tuyere, but it isn't that big of a deal to clean cold ashes with a shop vac. My forge had a hinged cover on the T-pipe, with a weight to keep it closed.

If you have never lit a coal forge before, there are all sorts of tips on how to use newspaper as kindling, etc. If you want to get right down to business, a small propane weed burner will get your coal glowing pretty quick.

kazander (author)2015-08-13

I like the design it looks functional and looks nice. I would recommend putting some metal pipe or something bellow it in a T so you can put the blower off to the side. This is so ash and stuff doesn't fall into your blower and break it.

Austin Noble (author)kazander2015-08-14

Thanks for the ideas. Blocking ash is the function of the vent cover, but a T pipe would definitely help to cut down on falling stuff. Good idea. Thanks again!

Nelly43 (author)2015-08-13

Nice 'ible. You did professional work on the forge.

M1chael 0 (author)2015-08-13

that's great.. I wanna build that !

AlyssonR2 (author)2015-08-13

A beautiful piece of work, and a well written commentary.

I would suggest a layer of limestone chippings on the bottom when you finally run it up - these will allow the heat to build up while keeping the bottom of the hearth relatively cool.

I have used plaster-lined forges, and you need to remember a couple of points:
* Take the temperature up slowly, the first time you fire it.
* Be prepared to wipe a layer of plaster slip across the inner surface every time you use it (the heat tends to reset plaster to the powder state).
* Mind out for the outer surface of the hearth getting HOT!
* Even if you use charcoal, a layer of coke at the bottom makes for a better air-flow.

Don't forget to comment on your project once you have started using it.

Austin Noble (author)AlyssonR22015-08-13

Thanks for the tips! They will come in handy.

bravoechonovember1 (author)2015-08-13

awesome first instructable!

sublingual (author)2015-08-13

Nice job, nice writeup!

And good on ya for pointing out that wet plaster/cement + forge heat = bad times ;)

RickJ5 (author)2015-08-13


CJStephens (author)2015-08-12

Looks like a very nice forge, great instructable as well! I have only ever made my forges out of cast iron, break drums, or brick. have you had any problems with this type of forge cracking or chipping at all?

Good question. This is the first forge that I have ever built, and it is actually still drying. I am curious to see how chipping resistant it is, after it has dried and I get a chance to run it a few times. About cracking, it is very thick and seems to be quite solid, and I doubt that it is going to crack. Thanks.

مدهشان (author)2015-08-13

nice work

BeachsideHank (author)2015-08-12

All very well thought out, should be a safe piece of equipment, nice work!

MatthewG26 (author)2015-08-12

Nice write-up, Austin.

dragonkilt (author)2015-08-12


seamster (author)2015-08-12

This is a great looking setup, nicely done!

About This Instructable




Bio: I'm a born again Christian. I'm going to school for mechanical engineering at South Dakota State University. I enjoy math, making things, drawing ... More »
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