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Do It Yourself Mini Forge

Years ago I had a small coal forge that I used for knife making and various other projects.  The forge was great for what I used it for, but was a pain to get fired up.  Not long ago, while looking on the internet, I came across a simple gas forge made from insulated firebrick.  Insulated firebricks, for those of you who have never seen one, are very soft and light.  The bricks are so soft in fact, that you can cut them with a knife.  The way that this forge operates is very simple.  A propane or Mapp gas torch (either works fine) is used to heat up a chamber that you have made inside of a couple of these insulated fire bricks.  Metal inserted inside the chamber will get almost white hot very quickly.  The chamber concentrates the heat and will get much hotter than a propane torch could on its own.  I will give a detailed parts list for and where to purchase the materials for this forge at the end of the article.  I purchased all the materials for this forge for approximately $58.00.  But, if you already have a propane or Mapp torch the cost will be considerably less.  Ok, time for step-by-step instructions for this useful little forge.

Wire the two bricks together as shown. The wiring not only joins the two bricks together but supports everything when or if the bricks crack during use.
First, I took two 9” L x 4 ½” W x 2 ½” thick insulated firebricks and with a spoon scooped out a ¾” deep and 2” wide x 7” long trough as illustrated in the pictures.  This will give you a 1 ½”x2”x7” long cavity when you are finished.   Like I said, they are soft.  You don’t have to be exact.  So don’t worry if yours is a little different in size and shape.  I try to make a somewhat rounded cavity.  Each brick makes up half of your forge.  Next, you will need to drill a ¾” diameter hole in the center of the cavity in one of the bricks.  A ¾” wood bit does just fine.  After drilling the hole, you will need to wire the two halves together.  Make sure you wire them up similar to the pictured illustration.  Wiring not only holds the two halves together, but the forge tends to crack with use.  It will most likely crack the first time you use the forge.  But, don’t worry; this doesn’t affect the forges operation so long as the wire has everything held together.

Drill a ¾” hole in the center of one of the cavities.

Here’s how I set mine up. Note that the tip is about an inch away from the small hole. I have it sitting on some common fireplace bricks because it does get hot.

After I finished wiring the fire bricks up, I set the forge on four common fireplace bricks and used a couple more to steady everything up.  Now, all you need to do is take your propane torch and aim it in the small hole in the side.  I used a conduit clamp bolted to a L-bracket to hold the torch.  The whole assembly is held in a drill press vice.  I use this set up because I can slide the vice back and light the torch then slide it up to the forge.  I can also easily disassemble it if I need to.  The tip of the torch needs to be about an inch or so away from the hole in the side of the brick.  Don’t shove it up in the hole.  The tip will get hot and possibly melt.

  1. Use common sense when using this forge. 
  2. Don’t use it in an enclosed space.  I only had the doors closed for photographs. 
  3. Make sure the tip of the torch doesn’t get too hot.  If it does pull it back from the forge a little.
  4. Keep the rubber supply hose away from the forge.  The forge gets very hot.
  5. Also, it goes without saying, watch where you place your hands.
  6. Keep small children away from the forge while in use. 

This forge is very safe as long as you watch what you are doing.  And as always, neither the author nor this web site is responsible for any mishaps.  Play at your own risk.

This little mini-forge will heat up to forging temperatures easily.  I use mine to make knives and jewelry as well as for heat-treating purposes.  For more information on these forges, or to purchase insulated firebricks, see Larry Zoeller’s excellent website at  He provides a lot of information on this mini-forge and larger forges.  He also sells most everything you need to construct one of these forges. 

Contact information:  

Larry Zoeller

4312 Lahnna Dr.

Louisville, KY 40216

502 439-0812

Materials List:

  • 2 – Insulated firebricks
  • 6 – Common fireplace bricks.  (Available at any construction supply store)
  • 1 – 3” L Bracket
  • 1 – Conduit clamp
  • 1 – Propane or Mapp torch (Bernz O Matic JTHZ)


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