How Do Swordmakers Temper Their Blades?

David Stifle

David Stifle

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Nov 20, 2008
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Last week I forged a 28 inch swordblade. Once I did, I realized I had to either send it out for HT or cut it back so it would fit in my kitchen oven. I ended up taking the blade down to 24.75 and shortening the tang more than I want. The whole thing will work, but the fact is, the end result isn't what I wanted, nor does it show folks what I am really capable of. So, can I built a tempature controlled kiln? Is that how well known swordmakers temper long blades? I would appreciate info, tutorials, etc., to steer me in the right direction.

Dave
 
David, get a 5" or thereabouts section of pipe/tube, about 4 foot. cap an end then fill it with oil then use a weed burner to heat the oil to the right temperature.
 
That's a really cool idea, Sam. I assume you have a thermometer inserted in the oil. So, all you have to do is check the temp, apply a little more heat, and just keep it there for an hour or so. Cool! Thanks a lot, I think I'll give it a try.

Dave
 
Low temp salt pots is the best way and high temp salt pots for heat treating. I have seen people use pipe cut lengthwise and filled with oil and placed on a gas grill. Stirring the oil will help even out the temperature. Just be sure to stay below the flash point of the oil.


-Xander
 
Over on the Bladesmith's Forum Boards (IIRC) there is an older thread by Dee, an Australian bladesmith lady who built her own electric sword tempering oven. It's a good WIP thread to read for building one.
 
I don't know much about them either.

I do remember Tim Zowada sells them.

Here's a link.
 
20 minutes tops to weld a base plate to a section of pipe and 10$ to fill it with oil, HF sells weed torches for 20$ also.
 
Sam's method seems right for my low tech (read that back yard) operation. Still, it's appealing to think of getting a bunch of firebricks, installing some type of electric heating elements with a thermastat control, and making a backyard thermostatically controlled oven. It would be good for a whole bunch of things, no? Pizza? Just kidding around, Sam opened my eyes to different ways of looking at this issue. Thanks Sam.
 
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Sam's got a point - you probably don't need the full on controls unless you are using salt for the heat treating part... quenching should be fine in warmed oil.
 
I do swords in the kitchen oven. Pull out the shelves and stick the blade in from the top right to the bottom left. Extra length can stick out. The door should close enough for the oven to hold heat. If you are worried about the heat loss, place a piece of kawool in the gap.
Temper for one hour and then turn the blade around so the sticking out part is now inside. Temper another hour. Remove and let cool to room temp, then repeat. A blade of about 36" will work fine this way.

I have clipped a temperature probe from a digital thermometer to the sword mid-oven and kept track of the blade temp while doing this. It works surprisingly well.
 
I have read different temperatures in my electric oven, near the element where the tip would be done your way Stacy. Plus, kaowool fibers in and near the oven I use for cooking is no bueno hehe
 
I don't use anything as a gasket, myself. But, kaowool is only a concern if it is blown about by a flame or air blast as small particles. As far as worrying about it being near the food, it is the same thing that is inside many oven walls, and non-toxic. The fibers should be of little concern in food contamination, but I agree that one should avoid getting kaowool all over the place. FWIW, kaowool's MSDS sheet does not list any precautions beyond avoiding creating dust, and only lists it as a normal mechanical irritant. They list nearly every item tested as a possible cancer risk., because everything ,including most drinking water, is listed are a possible carcinogen by the State of California.
http://www.fabricationspecialties.com/pdf/kwblanket_msds.pdf

I left out an important detail - My oven is gas, and I try and place the tip so it sits an inch or two up from the oven floor. I agree that an electric oven could be a problem. I used a thermocouple that could be clipped to the blade and checked different places on the blade. The end closest to the bottom got a bit hotter than the blade while the burners were cycling on, but quickly dropped back as the flame cycled off. The swing was about 15 degrees. The tip end ends up out of the oven for the second hour of each temper cycle, so the final edge hardness came out pretty even, with the tip perhaps a tad more tempered than the edge (which is not such a bad thing).

You could say that the tip ended up tempered at 415 for two hour and the blade edge got tempered at 400 for four hours.
The tang gets drawn soft with a torch later, and on a single edged, non-hamon blade, I often draw the spine down,too.
 
The best answer is a PID controlled salt or oil pot. Sam's weed burner will get you there but it will take A LOT of babysitting.

I am messing around with the idea of cutting a 3/8" wide x 3" high slot in the door of my Sugar Creek 24" kiln. I can slide a long blade through the slit and temper accurately. A Kaowool plug would do the trick when not in use. This would work for heat treating, too... as long as the cutting edge doesn't exceed 24"

David, what are you heat treating in?
 
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Rick,

I'll use my charcoal forge to Ht the blade, and quench in Parks 50 (yeah, I finally got some after losing 2 blades to water).
 
Sam Salvati said:
have you ever tried it? It's almost like ron popeil, set it and forget it. My rig held within 10 degrees for 2 hours.
Click to expand...

Interesting... No... admittedly I haven't tried it. Now... a flood of questions, buddy.

1. Are you using thickwalled pipe?
2. How long does the oil stay at temp between firings?
3. How do you maintain 10F using a weed burner? Are you running the flame up and down the sides of the tube or heating the bottom?
4. Where is your thermometer placed?
5. How is the heat being distributed? Is it the nature of the oil or are you agitating?
6. Are you using the gun on the blade? How often are you checking.

The gun is the only thing I don't have.
 
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An additional question for Sam, what kind of oil are you using and what do you reckon roughly is its flash point? I may have a sword to temper soon, this is interesting.
 
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