Because I use stock removal to make knives, I've never needed (or had the room for) a full-blown forge. However, I like to use tool steel for my knives and prefer to do my own heat treating. I started out just using a small stack of firebricks with pretty good results, but I did find myself using a fair amount of LP. So I decided to build a small forge for heat treating my folders. In fact I ended up building two but the most used one is a two-brick forge. Disclaimer: This is not the only way to build one of these, nor probably the best way. It's just how I did it. This is potentially dangerous! Please be sure you know what you are doing before you try to build one. Materials 2 insulating firebricks refractory cement wire or metal screen propane torch Warning: If you are planning to try one of these make sure you use the correct bricks. These are not the firebricks used to build chimneys and such. These are very light, soft, insulating firebricks like those found inside pottery kilns. Once I got everything I needed (those bricks can be tough to find.) I drew out a simple design. The plan was to hollow out two bricks as shown, leaving .5 to .75 inches of wall on all sides. Both ends have half circles cut out for airflow. When together, the holes are about 1 inch in diameter. In the top brick there's a small hole for the torch tube to fit into. The small holes along the edge are just dimples to help when I glued the two halves together. I used a pencil to draw out the lines on the bricks to cut. Again, these bricks are soft! You won't need a hammer and chisel. I used an Xacto knife to make the initial cuts in the bricks and an old spoon to hollow out the bricks. In the end the cavity inside was rounder and smaller than I had planned, but I think it was actually an improvement, and the extra thickness to the forge walls helps keep the heat in. I also made some adjustments to the openings at either end, making the front one slightly larger and and taller, and making the rear one a little smaller. I used a drill for the hole in the side where the torch goes. I made the hole just slightly larger than the torch tube. (Note: Originally, I put the burn hole towards the back, but after a bit of use I filled it and put another hole about three inches or so from the front. It seems to make better heat that way.) I checked the fit and scraped a little more until the cavities in the two halves fit together nicely. Then I put them together by buttering the edges of each with refractory cement and pressing lightly to get a good seal. I scrapped off the excess cement on the inside and outside and left it to dry over night. At this point some would just wrap some wire around the two bricks to help hold them together and be done. Since the bricks are so fragile, I decided to make something that would stand up to a few bumps and bruises. I had some metal screen from a window laying about so I wrapped the whole forge in that, nice and tight, and secured it with some wire. I cut out all the holes then put a thick coat of refractory cement over the wire making sure to force the cement down into the wire. I left that to dry for a couple of days. I ended up with something that looks like a really ugly adobe brick. But I've been using it for over a year and it does a fine job. With a short pre-heat it takes just a couple of minutes to bring the parts up to non-magnetic and I use only a fraction of the gas I did before. Here's a short video of the forge in action. It's a bit shaky but you get the idea.
