Building a Super Forge

[Mark Reich]

My first forge has been serving me well for basic bladesmithing, but it really isn't big enough or hot enough to do the type of work I want to do now. Hence, I decided to build something that will keep me smiling for the foreseeable future. 

I figured I would need a sturdy tube about 18" in diameter by 3' long. I called the steel yard to see what that would cost, and it was about $150. I didn't think that was too bad, but they told me to come down and look through the scrap yard. Low and behold, I spotted a commercial water heater that looked about right, and payed the scrap price of $15. 

With the bottom cut out, and the top cut off, it was Exactly the size I wanted. It even has double thick reinforced ends. 

I cut the burner holes and welded the drilled and tapped burner mounts to the shell. After grinding a thick layer of water deposits out, I finished the inside with 2000*F primer and paint to get a good bond with the 3000*F mortar that holds all the 2800*F brick and insulation together.

There's a layer of 1-1/4" thick, 4-1/2" wide brick, under the 2-1/2"x 4-1/2"x 9" brick. This is the actual floor of the forge. After learning how Sairset works (which is dang slowly), I let it dry for about a week.




1 1/4" x6" x9" brick are fully mortared in, to make solid walls instead of Kaowool walls. Now you can see the "subfloor" layer better. This solid, bonded foundation is absolutely critical. 




The outside layer of 2" Kaowool is mortared to the shell. It's slightly asymmetrical so I have room for an extra layer of Kaowool on the right side, where the burners are aiming. This will create a swirl effect to help eliminate hot spots in the forge.




It's pretty tricky to get all the Kaowool mortared together and supported into a nice smooth arch before the mortar dries. I'm pretty happy with the results at this point. 

High temp brick is very soft and fragile before the mortar soaks in and drys. It was easy to rip the triangular pieces with an old blade on the tablesaw. These will be mortared into corners to facilitate smoother transitions for a cleaner laminar flow of the swirling gases.




While I was welding the burner tubes, I also welded short pieces of angle iron to the outside of the shell on all four corners for extra strong attachment points for the legs. They really came in handy whenever we needed to move this heavy, awkward  sucker. There really wasn't another way to grab it without messing up the insulation.

After a few days to dry, I started running thermal cycles to stabilize everything. 
If anyone is interested, I can show more to this build