Mini-Forge

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I'm Mike, from The Geek Pub. I'm a maker. I love to make things. from woodworking to electronic...

A mini-forge is a fantastic tool to have around the shop. The mini-forge will allow you to make everything from jewelry to small pocket knives. It is an indispensable item for any shop where metal working will happen from time to time.

Bonus: Although not shown in this Instructable, this mini forge can be tilted on it's back and used to completely melt metals such as bronze and aluminum for molding purposes by adding a hardened steel kettle in the center.

Step 1: Watch the Video

Before you move on to the next steps, take a minute to watch our instructional video on making the mini-forge. This video has some neat tips and tricks that will make this Instructable easier to follow.

Step 2: Acquire the Components

You're going to need several items to complete this mini-forge. All of them can be obtained at your local big box home improvement center, or from Amazon.com.

1 Fire Brick
1 Aluminum Angle 1.5" x 1.5" x 24"
4 6" bolts, washers, and nuts

Note: A firebrick is made from a fireproof fiber material. This is not the same as a clay brick. A clay brick will be very hard to drill and work with, and will not withstand the heat of the mini forge. Firebricks are very light and easy to cut with regular tools.

Step 3: Cut the Brick and Drill the Holes

To get started, cut the fire brick into two separate but identical halves. (If you want a bigger forge see the notes at the end of this Instructable.)

In my case I used a standard 10" miter saw with a standard crosscut blade for woodworking installed. The fire brick is easy to cut and simple to work with. As always, wear a dust mask when cutting any materials in your workshop.

One brick will not get any holes. The other brick needs two holes in it. The first hole goes all the way through and needs to be between 1.5" and 3.5" depending on how big you want your forges mouth to be. Smaller forges heat faster, bigger forges work with bigger items. It's a trade off you'll need to make. The second hole goes through the side of the brick and connects with the larger hole. This hole should be the exact size of the nozzle of your propane or MAP torch.

Step 4: Add the Supports

Cut the angle down to the size of your brick halves plus about an inch. Then at each end drill a hole in the angle to allow a bolt to pass through.

Using the four six inch bolts, washers, and lock nuts, strap the two firebrick halves together, making sure the hole for your torch is on the left or right sides (not top or bottom).

Carefully tighten the bolts to make them snug, but no more. The firebrick will easily fracture if you over-tighten it. We're only looking to just hold the brick together and nothing more.

Step 5: Fire Up the Mini-Forge

If your torch has an arched neck you'll probably need to set your forge on a pedestal so that the torch will insert into the side hole correctly. If your torch has a straight neck you can just lay it on its side and set the forge on the a table. A cinder block makes a great pedestal.

Insert the torch into the forge about 1/2". Do not let the nozzle pass into the fire chamber as it will overheat and damage it. If you're torch has a lock on it, you can fire the torch up and set the lock to maintain the flow of fuel.

That's all there is to it! I purchased a set of 18" long needle-nose pliers to make holding items in the torch safe.

Some notes on the design:

1) Many have claimed the forge is unnecessary and items will get just as hot with the torch alone. This could be true if you are heating items that are longer than the forge or very thin. It is not true otherwise. The forge keeps a consistent heat on an item from all sides, which is why it is perfect for knife making and heat treating.

2) You can absolutely make this forge bigger by adding more layers to the forge. Just drill the center of on another brick and use longer bolts. This is an extremely common upgrade. Others have also added additional torches for more heat. Theoretically you could add an infinite amount of additional chamber bricks and torches if you needed to heat long rods for example.

If you enjoyed this project, you will probably like my others! Be sure to follow me here on Instructables! Also be sure to check out my website at TheGeekPub.com and my YouTube channel at YouTube.com/c/TheGeekPub!

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    38 Discussions

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    ThothLoki

    1 year ago

    Great job. Did you use k23 or k26 firebrick?

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    WayneEarl

    3 years ago on Introduction

    this is great!

    Question for you - by using the aluminum support, rather then something iron (support with a higher melting point), does this limit the useage of the mini-forge?

    3 replies
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    TheGeekPubWayneEarl

    Reply 3 years ago on Introduction

    The outside temperature of the firebrick is room temperature. You could make the supports out of plastic.

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    ScottK29TheGeekPub

    Reply 1 year ago

    Plastic? Who would have thunk lol. great project. I am currently researching to maybe do this too. I want to make something lol

    This is awesome, I have been looking for this very sort of project. I'm considering scaling it up. If our dear author has any ideas on scaling up to perhaps 2' square by 6" high, and temperature ranges possible within such an apparatus, at least one of us would be most grateful.

    My objective is to get steel & iron objects to temperatures approaching 1800°F, for forging and reheating, reforging, much as the ancient craftsmen made the Katana blades for Samurai by layering and merging layer upon layer many times, and then tempering them. (I'm leaving off the Seppuku blades, not going there!) I would like to study and work with making culinary knives, as well as custom blades for outdoorsmen - or should I say outdoors-persons. Locally to me, I have a muse in the iron working field, and can pick his brain. The furnace part, I'd need THIS PROJECT... I grew up in Charleston, SC, famous in small part for it's Iron Worked gates and fences.

    Thanks so very much, TheGeekPub . You nailed this one. Most excellent!

    4 replies
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    John T MacF MoodTheGeekPub

    Reply 1 year ago

    Sure will. I've got a lot of prep work to do this, and collecting parts. A year goes by, and I've made no progress.... It will take a little while longer.

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    ZaachariaJohn T MacF Mood

    Reply 3 years ago

    In my youth, we would go down to the Fisherman's Terminal (Seattle) and buy scrap propellers which we would cut down to fit into a 4" diam 8" deep crucible. Our forge was what looked like a 6" diam 10" deep concrete pipe closed at one end with a hole in the side (essentially this project scaled up a bit). A fan and propane was our fuel source - we cast a whole lot of items but as far as I know the only piece still extant is a bronze scarab belt buckle. I am pretty sure that the forge was purchased as a set. We did everything in a sand box that was 4' by 4' by 1'. We made a couple of frames to pack damp sand into to make molds. The melting point of bronze is 1742 F, the melting point of copper is 1,984 F - we dropped a penny into crucible with liquid bronze and the penny never lost its shape so that shows the upper limit for this type of forge. We probably could have melted the penny if we had lid. Propeller bronze was really, really difficult to finish - it took forever to cut, polish, file or do anything with it.

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    John T MacF MoodZaacharia

    Reply 1 year ago

    Sorry to be late replying. Modern pennies are copper plated zinc, so you can check the dates of the pennies, and perhaps get the copper ones. Zinc melts at about 413°C, and begins to boil at 918°C. So careful, VERY careful using pennies.Fumes from melted or boiling zinc can kill you.

    Pennies dated 1981 and earlier are copper, after, 1982, they began the copper plating of pennies made primarily of zinc. So be careful.

    Some say it's OK to use coinage in metal work, and some disagree. it's a dicey proposition, as technically destroying any form of US Currency Is a federal offense They have bigger fish to fry.. But pennies, well, they don't prosecute it, generally.

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    DirtGrader

    3 years ago on Introduction

    That looked like the drift for your Drill Press you heated hope you didn't beat it...Great Video and a very nice Clean looking Mini Forge... Thank You

    1 reply

    Part of my inspiration was this video, and being brought up where I was with iron work all over the city, Charleston SC, some of it hundreds of years old.
    "Raw Craft with Anthony Bourdain - Episode Four: Bob Kramer" on YouTube:
    Kramer made a knife so beautiful, I was inspired to investigate the primary tools of his work. Bourdain credits Mr. Kramer as the best culinary, perhaps the best knifemaker in the world.... Your video is spot on, TheGeekPub!

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    ybaggi

    3 years ago on Introduction


    thanks, cool simple project.

    Is this an aluminum silicate brick?

    Grant Thompson from The King of Random YT channel has used them.

    I like that but I am having a hard time (impossible) finding them in Europe.

    do other firebricks also cut so easily?

    cheers

    I like this tutorial because it gives me the opportunity to make an easy forge. I'm not useing it for metal though. I will use it for glass blowing applications,either way,very informative & easy to make..

    1 reply

    This is exactly what I was thinking - small scale casting. I have currently converted my microwave to a small kiln (about 4.5" circumference by 1.5" depth); I can cast small things (currently, skulls, hello kitty, and free-form puddles).