anyone use a kiln for heat treat?

V

vikingGoalie

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Aug 20, 2019
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so I might have an opportunity to pick up a amaco type 64 kiln for dirt cheap
I can't really find any manuals on it, and quite honestly i might just buy it and junk it because the tools/accessories/cart it's on are useful to me.
(school auction they are unloading this). So most likely I'll get this regardless, depends how it works out. But I am curious if anyone uses an electric kiln like this,
I can't find a manual for it yet, the temp gauge on it goes to 2500 F whether it can hit that or not, i have no idea. it certainly could be used for tempering.
 
Pottery kilns are not really right for knives. Besides being large, top loading, and power hogs, they are the wrong dimensions. If it an older model it probably has a kiln sitter control, so you would need to build a PID control and readout.

Some folks use one by cutting a small hole(s) in the top and hanging the blades on stainless wires. They cover the holes with kaowool and a fire brick.

Another use for a free or super cheap old kiln is to take it apart for the bricks and build a new knife kiln. Some of the electrical parts will work for a knife kiln.
The round lid also makes a good surface to set hot blades and do MIG/TIG/ARC/Torch welding. I put one about 30" round on top a cheap HF cart (bricks up) and store welding supplies on the shelves.
 
Adding to Stacy's points, I don't think many knife ovens can hit 2500F that are on the mainstream market, but that is certainly plenty of heat. My hottest recipe is 2050F so it would work for me. The trick is accurately controlling the temp in an even way, and accomodating your pieces....that's really the main difference in a "knife oven" and "kiln" in my shopping experience. One is designed for long and thin pieces, the other for larger geometric objects that can have some height. The steel won't tell anyone that it got it's "groove on" in a "kiln" if you don't 😊
 
I use an older Evenheat Gt 14-6 kiln for HT currently for simple carbon steels up to around 14" OAL. It maxes out at 1700 even though the pyrometer gauge says 2300 for the high end. I use a PID to control it. It can be done, but it's very inefficient (3 hours to get to 1700 degrees). I am going to start building my own HT oven soon to replace the kiln so its more efficient and better size/shape for knifemaking.
 
Today I went to help a friend clear out his grandfather's house. It will be demolished next week. The place is packed with so much crap it was hard to get into some rooms. The fact it was 96° this afternoon didn't make it any more pleasant. We had a list from family members to find things they remembered and wanted. The rest was ours to take what we wanted. Everything will be bulldozed.
There were a bunch of tools and some neat things I took, as well as ten nice Anvil Cases worth at least $200 each (look them up). The most obvious thing was that the old couple had gone into ceramic casting and firing of all sorts. The house had been converted into only one bedroom, a small kitchen dining room, and all other rooms were a full-blown ceramic shop. There were 100's of molds. Storage room had wall-to-wall racks to the ceiling with maybe 10,000 pieces in greenware and white bisque. An entire room for painting, a room for mixing and pouring slip with a big slip table sink, giant mixers, etc. The firing room was off the slip room. It had three HUGE kilns. The biggest was about 5-feet high and 36" round. The other two were about 48" high by 30" round. My friend says a ceramic person is coming to get all the stuff and equipment on Sunday. I hope they know that they will need 10 movers, some heavy dollies and hand trucks, as well as 100 storage bins to take it all ... and a moving van.
I should have taken a photo. We have a few last heavy things to get, so I'll get a photo of the kilns tomorrow.
 
You should try it. These are sensitive to the exact voltage 220 and 240 can respond very differently. Check your outlet and check the kiln and make sure the voltage matches. A 240 kiln running on 220 volts will be very slow. A 220 kiln running on 240 volts will not last long.

Someone on here will know the right terminology for this.

Anyway, cut a hole in the top and hang the blade after preheating the kiln. Cover the hole with ceramic wool.

Hoss
 
I'll add my 2 cents on this. Or rather, the opinion of the person who runs the ceramics studio at our makerspace. Ceramic kilns have relatively thin walls and build and as such don't like the quick temperature changes that happen when you open the kiln while hot. I suppose a small enough hole and being quick about doing this could work fine. They wouldn't let me use theirs when I was trying to heat color some sculptural pieces that wouldn't fit in our HT oven
 
Ok, I took a few photos. You can barely see the big kiln behind the other two because of the two feet of stuff on top. The floor is covered with ceramic pieces.
I added a few shots of some things we found. When was the last time you paid $0.71 for a box of 22 rounds? The Luger cartridges are also cool. The anvil cases are heavy and really strong. Long one is around 52X12X8", smaller ones are roughly 24X16X8".anvil case 6.jpganvil case 5.jpganvil case 4.jpganvil case 3.jpganvil case.jpganvil case 2.jpganvil case 1.jpg
 
I have a Skutt ceramic kiln with a sort of simple digital control. You can run programs, and I absolutely love it for carbon steels. It will do an anneal program very well. The max temp it will reach is 1750°F. It is also top loading, but you can very very easily get around that.

On the side of the Skutt, and with most kilns I think, there is a peep hole, and usually they come with a ceramic cone to cover the hole. Mine was about 3" above the floor on the inside. Using a hacksaw, I cut a slit about 3/8" of an inch side from that peep hole down to level with the inside floor. That extra hole does not impact the ability of the kiln to hold a very precise and accurate temperature at all. I simply slide the blade in, wait for the temp to rebound (takes about 15-30 seconds depending on the mass of the blade), and start a soak if the steel requires it. Once the blade is ready to quench, just grab the end of the tang with a pair of vice grips or pliers, and dunk it in the oil. Super fast from heat to quench, about one second. The only time I open the lid is to make sure the coils are still in place, and I also keep a bunch of scrap steel inside to act as a heat sink. This set up is just super awesome for heat treating carbon steel knives.

For high alloy and stainless, I use my Paragon.
 
Thanks Stuart.
That explains one thing I remembered about someone saying he cut a" mouse hole" in the bottom of his kiln and made a fire brick plug. I now see it was the bottom of the side. I guess as long as it is clear of the coils it will work fine.
 
BTW,
I do use a pottery kiln for HT. It is just not for austenitization. It is a smaller kiln that I cut a hole in the top and inserted a thick-walled stainless steel salt pot tube. I haven't used it in a while, but it was for niter-bluing hardware and damascus. I used the Brownell's NitreBlue salts (the ones that are melted, not dissolved). If you take them to just above their melting point. around 570°F it gives a neat antique patina look like old firearms. At 650°F (the max safe temp), a quick dip of a blade or longer dip of steel hardware gives a fantastic deep blue color. While far above the tempering of most knife blades, the dip is fast and does not seem to affect the temper significantly.

I initially used it for aus-quenching and mar-quenching experiments on bainite. My equipment and skills level didn't allow metallographic examination and simple hardness testing didn't show any advantages of what I did, so I let that go and worked on perfecting martensite conversion HT protocols. Maybe I'll return to tat study one day. Don't know that I will ever reach my initial goal of a bainite blade with a martensite edge, but some mix will be worth testing.

In the future I may do some research on quenching clayed blades into 400°F molten potassium/sodium salts, then in still air. It sounds counterintuitive, but I think the quench into molten salts at 400° could be almost as fast as a quench into 120° brine, and certainly as fast at oil. The lack of a vapor barrier is where it gains speed, and holding right at the Ms helps control the stresses. This could be an advantage that bears research.
A commercial salt pot oven is basically a pottery kiln with a long SS tube down the center. It has some extra electronics and shielding to be safe, but that is the basics. Knifemakers have made their own from free pottery kilns.

Salt pots are not for inexperienced makers and can be very dangerous, so learn a lot and visit someone who uses them before even considering making one.
Molten nitrate/nitrite salts become explosive above 650°F. an alarm or shut off control is needed to prevent a serious explosion.
 
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