I recently picked up knife making as a hobby and got obsessed with it It took me a few months to get all the needed tools and materials like a belt sander, cutting tools, drill and... a furnace for heat threatment.
First I started with small butane forges built in a coffe can like those shown here: http://www.instructables.com/id/How-to-Make-a-small-Gas-Furnace/
Eventually I found out that this setup is not strong enought to perform the heat-treatment (HT) on pieces of metal bigger than a couple of inches (5cm) due to the high dispersions and little efficiency of the design.
This was a show-stopper to me, since if I could not HT a blade it would never become a proper knife.
I could not use complex/risky solutions that involved any gas, since I tend to mess-up and gas is very dangerous to handle. I tought about inducion heating but this was kind of scifi to my possibilities and capabilities.
So, afther much research and test, I made my electric kiln. I had to do a lot of research to fill the gaps of the many things i didn't know. I found much help in ceramic/raku kiln makers since the base is quite the same.
I did not take pictures during the assembly of the project. Both because they did not seem to be that necessary, second I doubded myself that something good would ever come out if this and that it would ever work... Sorry...
I was cheap both in spending money and in quality, so the result, though it works, lacks a lot of design, security and might result in being dangerous. Use all the precautions and proceed at your own risk. High voltage is used here, without much of the needed protection. Please adapt this instructions to your need and add all the safety measures that you thing might fit into it.
Also this procedure requires the use of power tools, some of those (angle grinder) are VERY dangerous and can hurt you with non reversible damage. Please take EXTREME care when using those and wear all your protective gear: safety goggles, respirator, gloves, ear protection.
Step 1: Tools, materials and cost
1cm diameter wood dowel
pliers, screwdrivers etc.
papercups and stick
16 firebricks (for this design, your might need a different number)
1 small pack (1kg) of refractory mortar
4m stell "L" bars from metal shelves
nuts and bolts
some old computer cases (or any other sort of metal sheet)
Kanthal A1 Wire : 12 meters in my case.
3 (at least) ceramic whire couplers
electric wire and plug (rated 20Amps)
20 euros for the bricks and stone-wool
25 euros for the steel bars, nuts, bolts, anglegrinder disks
20 euros for the Kanthal A1 wire and electic stuff
0 for the metal plates
10 euros for the fire refractory mortar