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Scott A. Roush

Heat Treat Kiln Advice

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Well I finally just picked up a big top loading pottery kiln that I will be using for HT. It is 18" deep and 20" across. So big enough to do some long knives and short swords.

 

 

First... what methods do people use for holding their blades in the kiln? I will have some blades that would make sense to just hang.. but my longest blades may have to sit diagonally (it is 32" in that dimension).

 

Second... due to the large volume this thing takes a lot of time.. and probably money.. to come up to heat. the kiln came with a bunch of ceramic plates that are basically the same footprint as the kiln. I'm assuming these were used to take up space when firing smaller items since they stack up to about the spot that the second set of elements begin. So.. since I can turn on either the bottom or top set of elements.. does it make sense to stack this layer of plates and only use the top elements? Or even use both elements but reduce the space that has to come up to heat by stacking the plates? Or are the plates just going to be a gigantic heat sink and cause the kiln to take even longer? The more I think about it... I'm thinking the plates may have been used simply to bring the work piece closer to the top.

 

Third.. I am new to using a kiln for heat treating and am wondering what is the most practical method for reducing scale. Do most just use some charcoal to consume atmospheric oxygen? Or is it worth using one of the anti-scale compounds? Or just a thin wash of clay?

 

Thanks a bunch folks....

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Scott - I have the 36" deep kiln. I put a big cast iron pipe in it to add thermal mass, and I heat treat everything inside the pipe. I suggest something similar (a big cast iron or iron or steel box in your case so that the temp gradient from bottom to top is more even and the oscillations of the kiln temp flatten out very well).

 

You need the mass at both the bottom and the top, hence the big pipe or box to help conduct heat around and remove gradient.

 

I leave the tang a little longer and just drill a hole in it. This has cost me some drill bits due to the freakin' carbides in the w2 I love to use (I have been mixing w2 with Aldo's whc 1075).

 

I just cover the top of mine with kaowool, so I can actually let some of the tang stick out the top and clamp it in place.

 

Use much thicker wire than you think you will need. It will oxidize on you during the multiple normalizations and the slow ramp up to temps (especially when you put the big retort inside that you should get).

 

If the wire breaks (mine did) the red-hot thing will only fall an inch or so , but it will bend the poop out of it.

 

Great purchase. My ability with hamons VAULTED forward as soon as I got this kiln. I can't wait to get some shop time and go to it.

 

take care,

 

Kevin

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Thanks Kevin. Interesting you just cover the top with kaowool. I was wondering what I could do to heat treat full swords since I have the room to handle a 31" blade. Your solution seems like it would work as long as the kaowool is thick enough to hold the heat in.

 

So I could put a pipe in diagonally, place the blade in that, let the tang poke through the kaowool...

 

I wonder if I can get some stainless pipe and wire.

 

Do you add any charcoal to the kiln to consume oxygen??

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My kiln said specifically not to add anything to consume oxygen. The layer of oxides that form on the outside of the heating elements are important in maintaining their life. Consuming oxygen shortens their lifespan. I don't understand why, it seems like a paradoxical effect. But, the instructions from Evenheat say over and over again not to do that.

 

kc

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Hey Kevin,

What kind of kiln do you have and which model do you have?

 

Thanks,

Doug Adams

Jn 3:16

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At HT temps 1" of Inswool will hold in plenty of heat. 2" if you like overkill. Be careful if you use it loose as it sheds nasty little fibers everywhere. If you get inconel or monel wire to hage the pieces with you won't have to worry about the red strength.

 

Wayne Suhrbier

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