Toploading Kiln for heat treating

ScottRoush

ScottRoush

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Jan 10, 2010
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I now have a kiln I will be using for heat treating. It's got an 18-20" firebox (need to take exact measurement) and I plan to use it for heat treating larger blades.. and some smaller ones that will have a hamon.

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.

Also.. 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?

Then.. 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....
 
Scott,
What I was trying to point out is that a potter kiln has many problems when used as a HT oven. No one can really tell you how to modify or use yours, as we don't know much about it.....or what you are trying to heat treat.
Few knifemakers use one.

You can't eat up all the oxygen on earth, so putting in a piece of charcoal won't do much at all. On carbon steel blades you will have to either coat the blades with a wash of satanite or commercial HT coating, or just sand the oxides and decarb away after HT. Stainless blades will need to be wrapped in sealed HT foil packets.

You might consider selling the kiln to a potter or ceramics person, and purchasing a knife makers oven.
 
Okay... Got it. I guess I just thought my questions were general enough to apply to any toploading kiln with a deep firebox.

Just got great info and a lot of great ideas on another forum though. I'm actually pretty happy to have this now... many cool possibilities. I also finally found a thread where you recommended cutting a hole in the top and using wires to drop the blades in and out. Thanks for posting that ...

And thanks for the suggestion on selling it... but... that won't quite offset the cost of a new one :-) I have a new shop that needs to be heated and insulated (not to mention the coin I just dropped on disk grinder, VFD and MAP arm) and only so many upgrade funds. Must do what you have to do with what you have sometimes.. and I THINK this will be better than NOT having one.
 
Yes, it will work for the time being.
Make a hole and a fire brick cover. Use 10 gauge nicrome or stainless wire for the hangers.

Please be aware that any attempt to reach inside with tongs can be dangerous. Hanging the blades is the only practical method to use a pottery kiln.


Make sure you have the power to run it, BTW, those can draw some serious current. It will take a good while to get fully soaked before you can put the blades in - maybe an hour or two. If you stack up the kiln shelves, it may take even longer.
 
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I was a Kevin's Iron Age Challenge this past weekend. We did the tempering in the top loaders that he uses for his salt pots. He placed TC about 12-14" apart at different heights. The temperature variation was about 10-12 degrees.... and that was only the top 1/3 of the kiln! Unless you are using some sort of circulating fan(which Kevin tried) you will always get temperature variation. 25Degs can mean a lot... especially during a temper. What is preventing you from turning the kiln on its side?

I know it sucks to hear, Scott but the simple fact is hot air rises and if your set up does not allow the blade to lay across the same thermal plane, there will be uneven heating. We aren't talking hundreds of degrees(at least while tempering, austenizing temps could be more or less) so in the end, it only matters if it matters, right?
 
Well that makes sense Rick.. but I sure wasn't thinking there would be that much variation. I will have to do some experimenting tomorrow.

This kiln does have separate controls for the top and bottom .. so maybe some combination of different settings could even things up a bit?? But heat still rises.
 
That's what is good about making your own stuff, Scott... experiment and see what works.:thumbup: I would suggest paying close attention to those temperature layers.
 
well... now I'm looking at another smaller kiln that I have and am thinking about just using all of these soft bricks to build a long horizontal using the door on the smaller kiln. Eeegads.

I suppose a pipe muffle would just take on the same temperature gradient eh?
 
Yes it would. I feel your pain but am confident you will figure it all out..... and post pics, of course.:p

I am currently thinking about cutting a slot in my 24" kiln door to accomodate a 24" blade with the tang sticking out. A small modification but if I mess it up it'll cost me.
 
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Rick Marchand said:
Yes it would. I feel your pain but am confident you will figure it all out..... and post pics, of course.:p

I am currently thinking about cutting a slot in my 24" kiln door to accommodate a 24" blade with the tang sticking out. A small modification but if I mess it up it'll cost me.
Click to expand...

Instead of killing your original door, why not do a stack of bricks for a new temp door ?
 
12345678910 said:
Instead of killing your original door, why not do a stack of bricks for a new temp door ?
Click to expand...
The stand I have the kiln on will not allow it. It is on a roller cart for "economy of space" in my 8x13 shop... lol. I figure if I can make a 3/8" x 3" slot through the door, I could fill it with kaowool when not in use.

IMG_0088-2.jpg

IMG_0067-4.jpg


Scott, would anything prevent you from laying your top loader on its side and placing a few bricks along the bottom to hold your blades up from the coils?
 
Rick.... No... I probably could lay it on it's side. I will look into trying that. Although that wouldn't help heat treating the longer blades that would have to be oriented diagonally.

Ahh.. decisions.

Thanks for the picture and the advice Rick....
 
ScottRoush said:
Rick.... No... I probably could lay it on it's side. I will look into trying that. Although that wouldn't help heat treating the longer blades that would have to be oriented diagonally.

Ahh.. decisions.

Thanks for the picture and the advice Rick....
Click to expand...

I thought either the bricks or the elements wont take kindly to a horizontal position and do silly things like fall out.
 
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