Ceramic kilns for knifemaking?

[cramnhoj]

Hi, just wanna ask if ceramic/glass kilns I see on the pottery supplies websites are suitable for heat treating blades? I mean they also go upto 2300 degrees F, what's the difference between those and ones specifically labeled as for knifemaking / heat treating?

Has anybody tried using them for blade heat treating? Any info would be appreciated, thanks.

[Jamey Saunders]

The only two downsides to top-loading ceramic kilns are that they are HUGE, by knifemakers' standards, and are really a waste of energy. The other downside is that once you've finished soaking your blade at temp, you have to open the door, remove the blade, remove the wrap and quench -- QUICKLY!!!. When you open that top, all the heat rises out -- right where you need to put your arm.

If you can get around that, seems like a good choice to me. I use a small jewelry kiln, but it opens on the side like a knifemaker's oven.

[cramnhoj]

So you're saying if it opens in the front like knife making models it's pretty much the same? I was also looking into the Olympic 1214FL and 1818FL which are front loading kilns. There's also the Sugar Creek Big Knife Kiln. Anybody know if those kilns are good choices?

Also, if a kiln is advertised at maximum temp of say 2000 or 2100 degrees F is it safe to run it at 2000 degrees F or is it advisable to get something that's advertised at 2300 degrees F?

[fitzo]

I recently read that a lot of ceramic kilns are not intended to be opened hot, and are designed to be opened cool because the pottery can't take the thermal shock anyway. I don't know for sure, but it's something worth checking before purchase.

[Terry Primos]

Mine is a front loader, but I've known a few folks that used the vertical top loaders. To get around the problem of opening the lid, they cut a slot in the top of the kiln and lowered the blade down through the slot.

A fire brick is placed over the slot while the kiln is heating up. For hidden tangs (which is what these makers were making) the end of tang is clamped with a pair of Vise Grips, and the blade is lowered into the kiln. Then the slot is covered with Kaowool. After the blade has been removed and quenched, the slot is covered completely with a fire brick.

With this method the tang is left tough and springy. I suppose you could do a full quench full tang by lowering it into the kiln on a piece of wire, but that might be a little tricky when it comes time to take the blade out. I use carbon (oil/water quench) steels almost exclusively. If my primary steel was an air-hardening steel I would almost certainly opt for the front loader.

cramnhoj,
For one that was rated for 2000 degrees F. max, it would probably take a long time to get it up to temp. I don't know what you're heat treating, but if it is something that requires 2000 degrees F., I would probably opt for a kiln that is rated for a higher maximum temp. For me, the temperature range is 1450 to maybe 1600 degrees F. depending on what I'm doing. Once in a blue moon I might do an alloy steel that requires 1850 to 2000. My heat treat oven is rated for 2400 degrees F.

[cramnhoj]

I've talked with a guy who can custom make a kiln for me, he says running it at max temperature might shorten the life span of the heating elements. So I guess hardening at 2000 F is out of the question.

Nice idea about hardening only the blade leaving the tang out of the kiln. A note to others though, use it only for carbon steel and ones like O-1. Steels like A1 and stainless steels would actually have lesser toughness if differentially hardened. On a similar note, I was also thinking of what Fallkniven does, they forge weld a blade of VG-10 to a tang of 420HC or something. Guess it saves them in costs because only the blade would be made of the expensive steels. Makes me wonder though if the point of weld becomes a weak point? (Hmm, breakaway handle, hehe).

[Alex Cole]

I have one of the sugar creek HT/kiln ovens and for my HT it has worked fine. I got the smaller 110 version and it can take about an hour to get to temp but it has been a great little unit for the money.

I hope it helps.

Also I work with 01, 440c and ats-34

alex

[hammerdownnow]

A guard or bolsters can also work as a bridge and would alieveate any concern. Good normalizing is the key to a strong joint.