Heat treating in a forge vs a kiln...what is your preference?

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R.C.Reichert

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Is there anyone else here who just for whatever reason prefers heat treating the old-fashioned way with a forge? I was seriously thinking of getting an Evenheat kiln because I know you get more consistent results with an oven, but for me, part of the fun of knifemaking is just learning the skills and being skilled enough to be able to do this step myself, to see the transformation and the colors change in the steel. It makes me feel more connected to my work and connected to my ancestors than just sticking the steel in an oven and hitting a timer switch. Knives and swords were heat treated successfully for centuries without electronic kilns and survived through actual steel on steel conflict, but now it's seen as an inferior method of heat treating...perhaps because steels have become more high-tech. I like simple carbon steels. I guess I just like doing things the old way... it's kinda magical in a way. For me a heat treat kiln that does it all would take out the guesswork, but I think it would also kinda kill that magic too.
 
Hum where to start.

first let’s get one thing out of the way. A “kiln” is an oven used for pottery and glass work. We use heat treat ovens or furnaces. Second it’s just a heat source, it’s not adding or subtracting any magic. I can understand wanting to be connect with the process or connected with your ancestors as you say. But I can promise you 100% that those smiths of times gone by would use an oven over a forge any day of the week. Thy like most of use where using the best technology thy had available to them at the time.

Swords where no mythical thing, thy quite often got severely damaged. You can chock this up to a hand full of things like pore heat treat or steel lacking one thing or another. If anything I feel you are doing a disservice to ancestors past by not making the best blade you can like thy did. It’s one thing if all you have or can afford is a coffee can forge and a gallon of canola oil. It’s another thing all together to convince your self that a forge is good enough because you can’t afford an oven.

If I have learned one thing in my many years in this industry it’s that you need to be 100% honest with yourself if you want to improve. If your stone cold broke and getting by with a forge then more power to you. but own up to it and slowly work your way up the skill/tool ladder till you are producing the best blades you can. Don’t lie to yourself by shrouding old technology with a cloud of false information. Heat treating is probably the least exciting part of knife making. And trust me, if heat treating gets exciting then something went horribly wrong.

Oh and a heat treat oven is not a magic wand. It only does what you tell it. It’s not just pushing a few buttons. It’s hours and hours of testing coupons and adjusting temperatures and testing hardness. All ovens will have a heat gradient to them and could be more or less accurate then another. So just looking at some numbers that where posted on a forum will start you in the right direction but just like a baker it takes skill to turn a recipe into delicious food.

I can understand wanting to gain the skill of reading the colors of steel. But I can promise you many more experienced smiths then I have tried and failed. + or - 25° can make a big difference in properly heat treating a steel. If your using a trained eye you would be lucky to be within + or - 250°. The issue we have with our eyes is that thy auto adjust to conditions. You see it on every episode of forged in fire. You see smiths quenching liquid hot blades in oil. At proper temps with proper quenching oil A flare up is very rare let alone a fire ball the size I see on the show. Our eyes adjust so the longer you stare at the forge trying to hit that magic color you seen on the chart the darker your eyes adjust and the colder the steel looks.

I had this issue back in the day. i was trying to set some welds in Damascus. I sat there watching the forge and it just did not seam to hot that nice bright yellow I wanted to see. So I pulled the billet from the forge to try and set the weld and liquid ran off the billet and onto the floor. This liquid was melted steel but I would have sworn six ways to Sunday I was in the 2000-2100 range. I quickly rigged up a thermal couple to a pid display and tossed it in and it shot up to 2750° in a matter of seconds and error out. So yeah our eyes are amazing but thy are not all that good for judging temperature by looking at the black body radiation emitted from steel.

R.C.Reichert said:
Is there anyone else here who just for whatever reason prefers heat treating the old-fashioned way with a forge? I was seriously thinking of getting an Evenheat kiln because I know you get more consistent results with an oven, but for me, part of the fun of knifemaking is just learning the skills and being skilled enough to be able to do this step myself, to see the transformation and the colors change in the steel. It makes me feel more connected to my work and connected to my ancestors than just sticking the steel in an oven and hitting a timer switch. Knives and swords were heat treated successfully for centuries without electronic kilns and survived through actual steel on steel conflict, but now it's seen as an inferior method of heat treating...perhaps because steels have become more high-tech. I like simple carbon steels. I guess I just like doing things the old way... it's kinda magical in a way. For me a heat treat kiln that does it all would take out the guesswork, but I think it would also kinda kill that magic too.
Click to expand...
 
Yes I do ....
I prefer heat treating simple carbon steel’s and laminated steel in a forge because it is simply faster and easier to process. I’m referring specifically to Japanese white steel with high carbon and no soak and flash tempering

As far as I know there is no steel that processes faster than what I just mentioned And is easier to straighten
 
Like Habeer, I use my forge for many simple carbon blades. It is quick and I can get results equal to the oven.
I also do most swords in the forge …. because they don't fit in my oven.

With practice and some skill, a person can HT simple steels in a forge quite well.

The size and quality of the forge makes a big difference, though. It need a good refractory lining to allow the chamber to fully soak and radiate heat inside the forge. IT should have a good burner and the flame should swirl, not blast straight down in the center. Doing HT directly in the flame isn't a good way to HT.
A2BF, coffee can forge, or other simple heating forge will not HT well.
A well make 16" forge will work fine if you keep the blade moving and turning and don't overheat it.
A PID controlled forge will work almost as well as a HT oven.
 
Stacy E. Apelt - Bladesmith said:
Like Habeer, I use my forge for many simple carbon blades. It is quick and I can get results equal to the oven.
I also do most swords in the forge …. because they don't fit in my oven.

With practice and some skill, a person can HT simple steels in a forge quite well.

The size and quality of the forge makes a big difference, though. It need a good refractory lining to allow the chamber to fully soak and radiate heat inside the forge. IT should have a good burner and the flame should swirl, not blast straight down in the center. Doing HT directly in the flame isn't a good way to HT.
A2BF, coffee can forge, or other simple heating forge will not HT well.
A well make 16" forge will work fine if you keep the blade moving and turning and don't overheat it.
A PID controlled forge will work almost as well as a HT oven.
Click to expand...

Stacy,
I've heard that many sword makers will use a high temp lazer thermometer to check the temperature of their blades, is this something you've tried? How effective is this and would it be useful for knives?
 
I use both, but use a forge more often. That said, most makers tend to overheat a blade in the forge, it skates a file so it must be good. LOL
 
Low alloy steels have been the most sensitive to austenitizing temperature in our toughness testing. You can heat treat in a forge because you want to or like to or think it is more traditional, etc. But it isn't as good as a heat treating furnace.
 
When variance of 20f can result in losing performance in some steels, I could not consider heat treating without proper temp control. Tradition be damned. I warranty but blades for life, and promise the best performance the steel is capable of. I need temp control for that.
 
I use both... but when it "counts" I reach for the oven. Just this past summer, I taught "backyard heat treating" at a 3day blacksmith conference in Saskatchewan. It is entirely possible to HT your knives successfully in a forge. You have to be honest to yourself, though. It sounds as if you are trying to downplay the use of digitally controlled ovens. Why? There is no argument... they are more accurate and more consistent. The romance of bladesmithing is not threatened by technical innovation, it is bolstered by it.
 
Rick Marchand said:
I use both... but when it "counts" I reach for the oven. Just this past summer, I taught "backyard heat treating" at a 3day blacksmith conference in Saskatchewan. It is entirely possible to HT your knives successfully in a forge. You have to be honest to yourself, though. It sounds as if you are trying to downplay the use of digitally controlled ovens. Why? There is no argument... they are more accurate and more consistent. The romance of bladesmithing is not threatened by technical innovation, it is bolstered by it.
Click to expand...

I wouldn't be honest if I said it didn't have anything to do with cost either. Even the lowest of the totem pole Evenheat ovens I can get up here in Canada are just shy of $3000 and I am hesistant to buy the least expensive model they offer. I am going to assume they are quite a bit more affordable for people who live south of the border.
 
R.C.Reichert said:
I wouldn't be honest if I said it didn't have anything to do with cost either. Even the lowest of the totem pole Evenheat ovens I can get up here in Canada are just shy of $3000 and I am hesistant to buy the least expensive model they offer. I am going to assume they are quite a bit more affordable for people who live south of the border.
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I bought mine (22.5” model) over 5 years ago for about $2300. I haven’t had a failed blade since.

you can build one with parts from Auberins to make a good kiln for under $1000.00.
 
R.C.Reichert said:
I wouldn't be honest if I said it didn't have anything to do with cost either. Even the lowest of the totem pole Evenheat ovens I can get up here in Canada are just shy of $3000 and I am hesistant to buy the least expensive model they offer. I am going to assume they are quite a bit more affordable for people who live south of the border.
Click to expand...
I lucked out and got a Sugar Creek Kiln before they closed up. Less than $1000 for a 24" kiln.
 
R.C.Reichert said:
I wouldn't be honest if I said it didn't have anything to do with cost either. Even the lowest of the totem pole Evenheat ovens I can get up here in Canada are just shy of $3000 and I am hesistant to buy the least expensive model they offer. I am going to assume they are quite a bit more affordable for people who live south of the border.
Click to expand...
You can save a little bit of money by getting the Rampmaster controller. It works great.
 
I've used a forge, blowtorch, PID stuffed muffle in a forge and a furnace.

The furnace gave me by far the most high performance HT.

The knife edges were much better performance.

It takes more time to HT vs a Forge but the performance is worth it and I charge accordingly.
 
I have two furnaces and both are industrial lab muffle furnaces. One is a Lindbergh and one is a thermolyne. These furnaces are several thousands of dollars new

both in excellent and like new condition and purchased for considerably less than an evenheat.

and frankly I don’t think I would buy an evenheat given what I’ve read about the variations in temperature by users here

anyway my point is that if you look around on Craigslist and ebay you may find an industrial muffle furnace for a very good price. You have to be patient and it might even take a year to find the right one At the right price
 
The Evenheat furnaces work perfectly fine. The temperature variation is relatively small and comparable to more expensive furnaces.
 
R.C.Reichert said:
Stacy,
I've heard that many sword makers will use a high temp lazer thermometer to check the temperature of their blades, is this something you've tried? How effective is this and would it be useful for knives?
Click to expand...

Laser thermometers are not all that good above 1000F. I have a lab grade non-contact pyrometer that I still wouldn't use to tell the temperature of HT with. There are so many variables with the biggest being emissivity, and then there is scale, and maybe clay .... well you get the point. Using them for tempering and checking your oil quench tank is fine.

A few things to know about a laser thermometer:
The laser does not measure the temperature. It merely shows where the IR detector sensor is pointed.
The unit only reads the surface temperature, which can be higher or lower than the core.
The color of the object being tested, thickness, and degree is surface oxidation/scale/etc. will all affect the reading.
 
If I was to start again, I wouldn’t buy a furnace with as many programmable ramping settings. The pre heat and ramp feature is less useful for us knifemakers. Buying supplies to make two or three ovens where each temp can be set, and held would be more useful. Other than controlling cooling speed for annealing, ramping speed is always on max, and basically never used.
 
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