Pottery Kiln into HT Oven Question

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hiromix

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May 10, 2010
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Hello,

I’ve been scouring marketplace in my area, and there are Paragon high fire ceramics kilns out there for relatively cheap. I've certainly heard of people successfully using pottery kilns for knife ht, but I have two questions:

1. Is there a way to retrofit some kind of digital control measure? The kilns in question all seem to just have the low/med/high dial

2. Is this worth doing? The kilns are in the 400-600 range, so depending on possible solutions to question one, that could be cost effective. Or, should I just continue to save and get something ready-made?

My expectations would be that I’d be able to treat carbon steels and tool steels with relatively reasonable ht protocols. Wouldn’t necessarily expect it to be doing complex ramping protocols or anything.

Thanks!
 
Yes, it can be done. It isn't perfect, but works. It isn't going to work as well for knifemaking as a paragon or Evenheat.

First you need to convert to temperature control. Build or buy a controller that you plug the kiln into. Set the kiln on HIGH and set the controller to the desire temperature. It can be as simple as a PID, TC, SSR and some wiring and plugs. It can be as complex as installing a Rampmaster control. Most folks go with a PID kit. Look on Ebay or Amazon for PID kiln control kits with a 1/8" or 8-10 gauge TC. You want a 40-amp, TC with a heat sink and probably a cooling fan.

If you don't understand the above, get someone who is familiar with this to do it for you.
 
One thing I learned recently from the head of our ceramics guild is that ceramic firing kilns are designed to kept closed during heat up and cool down and should not be opened when firing. They claim that the rapid cooling that happens when you open the kiln (mostly top loading with huge openings where all the heat can escape) will shorten the life of the electronics/heating coils.
They wouldn't let us use it for HT tools while we were re-wiring our HT oven...
 
Thanks for the replies, guys. I have some local guys who own knife ht kilns, so I may just stick with that. Want my own setup, but clearly being patient and getting the right kind of equipment is the better option.
 
Weo is right about not wanting to open a hot kiln. It is not a pleasant thing and can set your shirt sleeves on fire easily.

The way around opening a kiln is to cut a round or square hole in the top and hang the blades on 10-gauge stainless steel wires. Make a plug from soft firebrick for heating/cooling the kiln and cover the hole with a folded piece of kao-wool during HT when the blades are hanging in the kiln.
 
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Stacy E. Apelt - Bladesmith said:
It is not a pleasant thing and can set your shirt sleeves on fire easily.
Click to expand...
Thanks for pointing out the personal safety thing, Stacy. I wasn't even thinking about that.
Perhaps I should rethink my shop orientation spiel about the importance of adopting safe shop practices because tools don't heal on their own unlike people...🤔


nahhh, the tools need a voice too.😜
 
Don't ask how I know about setting your shirt sleeves on fire.

Ok, I'll tell you. It was taking a crucible out of a melting kiln. Pretty much the same as an open pottery kiln. Set one sleeve on fire in a split second.
 
Building your own oven isn't too bad to do; I built my own this summer!

I also converted an older Evenheat GT 14-6 to a HT kiln by using a PID, SSR, heat sink, Thermocouple and an extension cord I cut in half. I wired it so I would plug one end of the extension cord into the outlet, then used that to power the SSR/PID/TC and then wired the female plug end of the extension cord to plug the kiln into. Worked pretty well, but I needed longer blade capacity and higher temps to do stainless.
 
See the current toaster oven conversion thread for details on doing a conversion.
 
Found my wiring diagram to make the control box for a 110V kiln to run with a PID. Thermocouple wires went to #8 and #9 on the PID in this case:
gPbi05E.jpg


In use:
6UdEow5.jpg
 
Pretty much identical to what I make. I also use cheap toolboxes for HF for the case. I add a cheap surplus computer fan to the box for cooling the heat sink.
 
hiromix said:
Thanks for the replies, guys. I have some local guys who own knife ht kilns, so I may just stick with that. Want my own setup, but clearly being patient and getting the right kind of equipment is the better option.
Click to expand...

If you have access to HT ovens via friends, I’d use that until you can get the money saved for your own. I messed with rigging up various kilns with thermocouples and PIDs and it’s just a royal PITA.

I got a Paragon and I love it but a buddy of mine picked up a new Hot Shot for half of what I paid and it works really well so far.

Pro Tip: Toss your friends a few bucks here and there or maybe gift some handle material now and then for using their ovens. They may not expect it but it’s a class move. A friend who used mine gave me some scales to say “thank you” and it was really cool of him.
 
I agree, most folks with a proper HT oven are glad to help other local smiths with HT. My machinist knifemaker friend trades me machining tasks for HT.

As far as using a pottery kiln for HT in a hobby situation, it is not a simple thing. For a full-time shop doing dozens of blades, it is somewhat common.
Benjamin Kamon has a large pottery type kiln in his shop that he converted and added a top port with firebricks. As he pointed out in our interview, it takes at least 3 hours to heat up and overnight to cool down. It also draws a LOT of power.
 
Heh, my Heat Treat Oven takes like 3 hours to get to 2150, so I know that feeling! I am going to re do it with actual K23 bricks this year (mine weight 2.8# each instead of 2-2.1# each and there are over 30 bricks!) and turn the old one into a tempering oven.
 
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