Introduction: 2 Brick Forge

Picture of 2 Brick Forge

I have been looking for a 2 brick forge design for a while and couldn't find any that met my needs. Most are 1 Brick Forges that are really too shallow for what I want to do.

I am working on longer pieces of 1/4 and 5/16th stock at about 5"-7" lengths.

This is my parts list:

  • 2 Fire Bricks 9"X4.5"X3"
  • 1" spade bit
  • 5/8th spade bit
  • 5/16th drill bit
  • Cold Chisel
  • 36" 5/16 - 18 threaded Rod cut into four even pieces 9" long
  • 16 5/16 - 18 nuts
  • 8 split washer
  • 4 one foot length 1"X1" steel angle stock
  • Power Drill

I decided that I needed an 8"x3"X3" chamber, so I marked the brick with a permanent marker.

Step 1: Drilling

Picture of Drilling

Using the 1" spade bit, I drilled out a honeycomb from the soft brick to a depth of about 1 1/2". I marked the spade bit to how deep I wanted it to go.

I took my time because of the soft nature of the Fire Brick, I didn't want to crack it.

Once I drilled out the chamber I used the 5/8ths bit to drill the hole to insert the burner.

Using the chisel as a scraper, I smoothed out the chamber floor and walls.

Step 2: Brackets

Picture of Brackets

I drilled 2 holes on either end of one side of each angle stock. The stock should extend about 1 1/2 " past the brick.

I used a nut/split washer/nut method to measure out the leg height and locked the nuts in place on one end of each of the threaded rods. About an inch high.

Step 3: Final Assembly

Picture of Final Assembly

Sliding the rods threw the holes and bracing each side of the bricks, sandwiching them together, thread the remaining nuts in the same nut/split washer/nut assembly to secure the brackets around the bricks.

Step 4: First Burn

Picture of First Burn

Light and slide your propane burner into the hole on the side.

When I did the first burn, there was also a dust cloud from where I didn't get all the dust from the scraping out.

Also, I have read that a lot of these fire brick forges tend to crack during use. Most instructions that I read recommended just wiring the brick together. I thought that wouldn't look nice, which is why I went with the angle stock brace.


RyanRamos98 (author)2016-02-27

I would have put like 2 or three burners on top would you think that works better? Ive seen some brand name forges with a similar structure but with the burners on the top

squirejoe2 (author)RyanRamos982016-02-27

The reason I went with the side for the burners is because I was lazy and didn't want to figure out a bracket so they wouldn't fall into the chamber. I can't think of a reason it wouldn't work from the top.

About putting 3 burners in, due to the size, I would be worried about structural integrity. The fire brick I used was very fragile and can crack easily from significant thermal changes. Mine has cracks from usage. Adding a 3rd hole might be too much, but that is just my opinion. I have not tried it.

The bricks I used were only about $6, so I wasn't to concerned about breaking a couple, so I would say go for it. If it works, AWESOME! If it fails, at least you learned something.

apowell25 (author)2016-02-24

i love this. wondering if you can fill the back with coal in opposition to propane using a hair dryer to supply oxygen as seen in other instructables.
My plan is to try just that. ill take pictures and credit this post

squirejoe2 (author)apowell252016-02-25

Go for it and let me know how it goes.

The only drawback that I could see is that the chamber is rather small. The amount of coal you would need to get the metal hot enough might take up too much space and you would be constantly feeding it.

sammcleod97 (author)2015-08-17

love the simplicity to it.... but I'm seeming to have some trouble drilling out the hole. Can I get the manufacture of your bit?

squirejoe2 (author)sammcleod972015-08-17

Here is what I ordered from. You might be able to find the bricks somewhere else cheaper, but they have always sent me exactly what I was ordering within a very reasonable amount of time.

Where I ordered from:

What I ordered:

CodyL4 (author)2015-06-17

super awesome! easy design but I seem to be having some trouble with air flow. the air inside isn't circulating enough oxygen to keep it lit. I'm using a propane torch but it'll only burn for a couple seconds. I'd rather not have to drill more holes to allow air in unless that is what I need to do. any ideas on how to solve that problem?

squirejoe2 (author)CodyL42015-06-17

The torch that I use has O2 holes behind the end of the burner. I have not seen that issue, myself. This is the torch head I am using.

CodyL4 (author)squirejoe22015-06-17

I figured it out. I was too ambitious with the flame size. thanks for the reply though.

squirejoe2 (author)CodyL42015-06-17

awesome. let me know how it works for you. I am debating on drilling a second hole 1/2 way down for a second burner. I will update this if I do that.

knutknackebröd (author)2014-12-03

slightly on topic; any dutch people who know where to get these "fire bricks"??? or at least a proper translation? and nice ible !

I'm from the Netherlands, and quite a while ago we built our own fireplace. We ordered some fireproof bricks from this site:

Depending on where you live you might want to consider stopping by there. Living in Brabant, I've got one quite close to me.

Hope this still helps you, if you haven't yet found what you were looking for.

thanks for the input, but the problem is there aren't any shop nearby as far as i know and the shipping cost is often twice as much as the order itself!

I'm from the Netherlands, and quite a while ago we built our own fireplace. We ordered some fireproof bricks from this site:

Depending on where you live you might want to consider stopping by there. Living in Brabant, I've got one quite close to me.

Hope this still helps you, if you haven't yet found what you were looking for.

vuurvaste Brick ?

isolatie van de baksteen ?

I am using Google Translate, so I hope that helps?

Also Kiln Supply shops for Ceramics.

haha quite commical translations, these are really litteral and probably will just get you funny looks if you ask for them in a store:P thanks for the input though!
ps. might be a good idea to look into ceramic shops

Happy that I could make you smile! :-D

Good luck!

M2aestro (author)2014-12-06

I really like the free-standing nature of the legs for this thing, and would remind folk not to leave this on a wood bench or against flammable materials...don't laugh, I've seen that done with older torch pots!

Stephen White (author)M2aestro2014-12-28

An inch or three rise protects tables well. A couple of 3/8" nuts make cheap feet on the All-Thread rod and also barely fit in 1/2" Electrical tubing if you tap it with a hammer. Slide EMT tubing into a 3/4" hole bored most of the way through a piece of wood for cheap, no-scratch feet.

squirejoe2 (author)M2aestro2014-12-07

Good Safety tip. I intentionally put it on taller legs to allow airflow.

From what I have noticed so far with mine, is that the brackets do not get warm after using it for over an hour. This is my experience, but I also have it setting on 2 of the same type of bricks, just as a precaution. Working with different types of forges from Coal, Charcoal and Gas...Safety is always #1.

Also....I have a fire extinguisher withing 5 feet of the work bench...again....Just in case.

michael.r.honsa (author)2014-11-30

Do you know how hot this gets?

don't put your hand into it when it's burning.

I don't have a thermometer that reads over 800F. I am not sure how hot it would get. I would think it would depend on the gas. I am using Propane.

Here is a link to the different temperatures different gasses burn at.

M2aestro (author)2014-12-06

Remember that your product will be different from those made in charcoal forges...unless you are pretty clever about your flame, you'll not get any carburizing of the metal surface with mild steels, if you are working with those.

This appears to be an approach (the torch burner) suited to short pieces, or to short sections of longer parts. A replaceable brick door in the back would allow feed-through of longer parts.

Jacobleroy (author)2014-12-03

Hey. Good idea.

Please elaborate on the "propane burner" not sure exactly what u r using.

squirejoe2 (author)Jacobleroy2014-12-03

The one I am using has a hose between the tank and the burner, but here is a link to what I was envisioning:

Jacobleroy (author)2014-12-03

Hey. Good idea.

Please elaborate on the "propane burner" not sure exactly what u r using.

tnetcenter (author)2014-12-02

You will want to use extreme caution AND a dust mask or respirator for this project. The dust from fire brick is real bad for you to breathe!

squirejoe2 (author)tnetcenter2014-12-03

Good safety tip. Thanks!

omega_entity (author)2014-12-02

Question! Do you think this kind of setup would work well for doing wax burnouts and melting low-meltpoint metals (for small-scale casting)?

squirejoe2 (author)omega_entity2014-12-03

I guess....I have never done the burn-out of Lost Wax Casting, and I wasn't taking that into consideration in my design.

snoopindaweb (author)2014-12-03

Thank You. ~(:-})=

PopsicleGhoul (author)2014-12-02

Great Instructable! I hope your blacksmithing goes well.

Where did you get your firebrick? I have been looking for them in order to build a microwave furnace and an electric arc furnace. Thanks!

squirejoe2 (author)PopsicleGhoul2014-12-02

I ordered them from Sheffield Pottery, but if you look up Kiln Supplies you might find something local to you. Also eBay sometimes has them.

DanielB12 (author)2014-12-02

How hot can this thing get?

squirejoe2 (author)DanielB122014-12-02

I don't have a thermometer that reads over 800F. I am not sure how hot
it would get. I would think it would depend on the gas. I am using

Here is a link to the different temperatures different gasses burn at.

AgentRed1 (author)2014-12-02

Ummmmm. What is this FOR?! :-)

squirejoe2 (author)AgentRed12014-12-02

Heating metal for small scale smithing. I will post what I make when I get a chance.

13bigred13 (author)2014-11-29

Have a similar situation (coal-fired forage not allowed), so new to this gas powered stuff. Need a bit more internal space, so going to try a 4 brick design, but my question is what type of burner/regulator do these mini gas forages need?

squirejoe2 (author)13bigred132014-11-29

Just the burner from a regular blue canister Propane tank from Home Depot. You can get fancy, but for me, this does the trick.

robbied (author)squirejoe22014-12-02

The MAPP gas one burns slightly hotter, but if yours can heat steel to the point you can forge it, then that's enough :)

robbied (author)2014-12-02

That is a great idea. A little more versatile than the one brick, as long as you can get enough heat into the larger volume.

Good work.

marhar (author)2014-12-02

Neat idea! It never occurred to me that fire brick would be drillable like that.

abinc (author)2014-12-02

Another point: Firebrick is cast in various shapes by refractory manufacturers. They may not be locally available but with a diamond or bonded carbide rotary blade, you can cut rectangular bricks into wedge shapes and use them to line a circular can or drum, such as a 5-gallon pail. If you then drill a hole tangental to the interior at one end and angled toward the other end for the tuyere (or burner nozzle) to enter, you will get a spiral of heat that will be pretty uniform throughout the furnace. Of course the ends of the can need to be lined with firebrick too! Cut another tangental opening at the far end for the stack, if the furnace is to be used horizontally. If vertical, your stack can be incorporated into the cover. The cover, also, is firebrick but would be square in shape and fits loosely over the top of the can. That allows angle stock to be used externally to hold the bricks together: you don't want iron inside the furnace!

squirejoe2 (author)abinc2014-12-02

Sounds like you have a lot of information to share. Have you thought about doing an Instructable? I would love to read how you do things.

Jakes workshop (author)2014-11-28

wow nice work
Do you know how hot is it or can you melt aluminum in it?

I don't have a thermometer that would reach over 800 degrees, so I am not sure how hot it can get. My thought is that it will get as high as the gas you use. I was just using propane. You can Google the different gas temperatures.

abinc (author)squirejoe22014-12-02

I notice that you have several questions relating to temperature. The easiest (and inexpensive) way to measure temperature is to use "slump cones." These are normally available at ceramic supply stores. The cones are fabricated of differing amounts of silica and alumina. They will sag or "slump" at different temperatures so the artisan can estimate how hot their furnace gets under varying conditions. Otherwise, use a platinum-irridium thermocouple with analog pyrometer to read the temperature.

abinc (author)2014-12-02

I've built several furnaces. One was made of silica board and was electrically heated to use as a glass annealing oven. The others were mainly reverberatory in which the heat from the burner is reflected off the side and top walls. It has a separate chimney to facilitate access without undue danger to the worker. The material of construction is fire brick, and it is not soft. It lasts. I used angle iron and threaded rod to support and lock the brick in place (outside the furnace, of course). A carbide saw or hole cutter is needed to form the openings for the burner and stack. My designs were limited in size by the dimensions of the fire brick. The benefit of the design is (a) ease of fabrication, (b) size, (c) and most importantly, fuel economy. The brick is a good insulator and the design allows for maximum heat input to the metal being worked. Study up on reverberatory furnaces (17th century technology) before building your next one. You'll be pleased. (By the way, an inexpensive way to achieve constant temperature is to calculate the heat loss compared to the heat input for the size/shape of the furnace. When balanced, the temperature inside stays constant without the need for thermostatic controls. While satisfying to build and use, I think if I were to make that type of furnace again, I'd use an Arduino controller.)

jkyas (author)2014-12-02

Nice simple design. I'd be interested in what you are making in the thing.

Instead of wiring, you could use a couple of stainless steel straps (like the plastic carton reinforcement, but SS.)

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