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: https://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

angle grinder
1cm diameter wood dowel
pliers, screwdrivers etc.
Google Sketch-Up
metal file
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
stone-wool insulation
some old computer cases (or any other sort of metal sheet)
Kanthal A1 Wire : 12 meters in my case.
metal wire.
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
<p>So are you using this to harden your blades as well? You had only mentioned the tempering temp which was 900 degrees, which is way too high for tempering and too low for hardening. You do realize that your blades must be hardened before tempering...</p>
Sorry, bad translation... in Italian you use &quot;temper&quot; instead of hardening.<br>So yes, I use it for HARDENING my blades, while for tempering I use my regular kitchen oven. Grades are Celsius. 900&deg;C are more than enough to harden a blade. It depends on the type of steel. <br>C70 steel (similar to O1) gets non magnetic around 770&deg;C and reaches the perfect hardening point around 830&deg;C.<br>What I can't do are only inox steels.
<p>Hi Buddy, seems you already answered &quot;that guy&quot; :-)</p><p>Anyway, just wanted to say that I am in the same boat as you, I had very little money to start, I had to make my own 50mm x 1800mm belt grinder, and my forge etc, you have done an excellent job here and I wish you all the luck in the world with all your endeavours, including knife making</p><p>All the best,</p><p>Pete</p>
<p>Hey fella, he's talking Celsius not Fahrenheit, he has plenty of heat for the heat treatment of blades ;-)</p>
<p>Very cool! Couple questions. Where did you get the ceramic wire coupler? How did you wire it up to the wall? </p>
Hi !!<br><br>I got the couplers in the same shop I bought the Kant al-A1 wire<br>I'm not sure you actually need a ceramic one... I guess that a normal 100% metal coupler would work as well. <br>I put the coupler close to the wall of the oven, so to have the resistance inside and the electric wire out.<br>The only thing I'm not sure about is how not to let the heat pass fromt the resistor coil to the electric wire...<br>Anyway take good care in selecting the right brick: pick light insulation brick, mire are wrong and cause the oven to heat tooooooo slowly.
Even though you are making another,I still like this.I know you are in Italy(I'm in USA),so I don't know what you have available,but here you can either get a cheap tile saw(wet or dry) at Harbor Freight,or we have many hardware stores and plain old rental stores that rent wet tile saws cheaply.This will keep the dust down,and be much easier.Also,I've found in doing projects like this,it's easy to get a masonry blade for a circular saw,cut the 2 grooves,and just use a cold chisel to break out the center.Still makes dust,but at least it's controlled by the dust chute(still do it outside),It's a lot less messy than the angle grinder.Hopefully,this info will help others tackling such a project.
Thanks a lot for your notes. I'd never think about renting those tools, first of all 'cause i don't know if I'd be able to use'em. <br>Still the main reason I'm making a new one (I'm very late on that one since too much life got in my way) is that those bricks are completelly WRONG. They resist to the heat but do not isolate heat. Thus the most of the energy is wasted in heating up the brick !! No surprise it takes up to 4 hours to get to 850&deg;C...
Nice Idea!! It should avoid the need of carving the grooves to store the coil inside.<br>Still the material needs to resist 1000&deg; (C) and be NON conductive (to avoid the risk of shortcircuits should the blade fall on the side and touch the coils)<br><br>What materials are they made of? ceramic?<br>I've also seen ceramic rods ued to wind the wire aroud to keep them straight once the temperature makes them soft.
just out of curiosity, where do you come from, you said euros, so i thought he might live in the same country as i do, i live in the netherlands
I'm from Italy.<br>Forget this 'ibel anyway. Afther using it for a few months I can say that it work... but it's way too inefficient to consider it using &quot;for real&quot;<br>I'm working on the next one that will be much better. Hopefuly will be ready for the spring.
last year i had been refurbishing a neglected kiln that i picked up for $200, and flying this blind i didn't know what elements that i needed being that it seemed that their were so many choices...all in all i figured it out eventually after getting very little help from a dude at duralite inc. lets call him RICHARD or dick for short... i figured out i could roll my own 8 elements for $65 rather than $380... in a matter of minutes using nothing more than a 3/8 &quot; rod, a drill and a fixed position bearing mount... needless to say this will save me tones of money in my life
We,ve got a kiln and the coils are held in by heat resistant 'U' wire. <br>It's quite cheap to buy from glass supliers.
is there a reason why you decided to make your own heating elements as opposed to buying premade ones? i'm looking at making a ceramic kiln and there's a lot of options out there for heating elements that are relatively cheap.
well, there are different levels of &quot;cheap&quot;<br>I made the elements using the A1 wire and it cost me about 20 dollars in TOTAL. <br>Plus this way I was free to have them the exact size/shape/scale/diameter/lenght I needed them.<br><br>Afther building it the main advatage I see in having pre made elements is that you don't have to cut the grooves in the bricks to set the spring into, saving a lot of work, noise, dust and maybe even your lungs...<br>Still this way you have to design the kiln around the elements
Hi, I'm very interested in building one of these myself for knife making. I have been doing some research and I found a website which sells electric kilns and also provides data on them. The smallest one they make is ten times bigger in volume than yours and it has a 2.3kW power rating and is rated to a maximum of 1300&deg;C<br> <a href="http://www.furnace-eng.co.nz/Kiln%20Sizes.htm">http://www.furnace-eng.co.nz/Kiln%20Sizes.htm</a>&nbsp;<br> <br> I don't know if this is at all useful, but hey.
thanks for the advice, new infos are always appreciated
Thank you!<br>I'll have a look at it and see if there is any good advice I mighjt use
you may also want to look at getting a PID to control the kiln. The instructions for mine gives you a sample scenario of using it in with electric heating elements in a kiln.
Thank you!<br>That actually goes for version 2.0 ... someday

About This Instructable




Bio: DIY Addict, like to solve problems, do thing with my hands and find the cheap way around my needs.
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