Knife heat treating recipes

[Bucksaw]

We'll, my oven came in today. I opted for the "Knife Dawgs" oven by Paragon, offered exclusively by USA Knifemakers. QuickDraw is supposed to help me get it all wired and up and running within the next week or so.

My question is, what are some good heat treating and annealing recipes to use for my blades? Most of you know that I use old sawmill blades,but I am going to play around with some files and rasps, leaf springs, and even some other odds and ends that I have laying around. All of it is high carbon steel, but can it all be treated the same?

What are some recipes that might work for me (temps, soak times, etc.)? Any help at all is appreciated.

[Bucksaw]

Anyone?

[Jason Fry]

I think I can link this here. If it gets axed, maybe I can copy/paste the content later.

http://www.frycustomknives.com/tutorials/heat-treating-instructions-for-common-knife-steels

[Jason Fry]

Aside from the general instructions I linked to, with mystery steel, 1475 or 1500 with a 10 minute soak, quench in 125-150 degree canola is a good starting point. If you end up with a usable knife, you can tweak your process a little. How hot you have to temper to get a stable edge is a good telling point. If you get an edge that wants to roll a little at a 325 or 350 temper, you're not getting hard enough. At that point, it's either the steel or the quench oil.

[Bjankowski]

Remember too that old files are made out of 1095 or W-1 which do require a soak time of ten minutes at 1475 (after normalizing three times) and a fast quench. Best to use Parks# 50 or brine which I prefer. The temp needs to drop 800 degrees in one second, the other oils are too slow.
Some people cringe at using brine for fear they will warp or crack a blade, but if you control your temp you won't have an issue. I've done tons without any problems, enough salt in your water to float an egg and I bring my water temp up to 150-160 degrees.
That high of a carbon content in 1095 and W-1 it's easy to over heat and cause gain growth. The carbon content in 1095 is .095 -.104; 1084 is probably the easiest steel to work with in my books. I call it the AK-47 of steel!

[Jason Fry]

I think Jank is right on with the file HT. The brine part is scary to me, but makes sense

If you're going to start buying steel, buy 1084 or 1080.

[Bjankowski]

BTW Bucksaw congrats; good investment for every knife maker you won't be limited to the types of steel you can heat treat! Good job!

[Bucksaw]

Thanks Jank. I do have another questions though. While researching the topic I have seen a lot of references to "normalizing" metal. Im not entirely sure what that does, when it should be done, or at what temperature (I assume its a heating process).

Im gonna start researching the 1090 and W1 steels. The brine doesn't scare me too much, because it is my understanding that the W designates that it requires a water quench. From what I can tell, as long as you use the proper quenching method, warpage and breakage isn't a problem.

However, Im still unclear on air quenching. Does that just mean cool naturally at room temp, or do you have to use a blast of air, stick it in the freezer, etc?

[Jason Fry]

While you'll see industry references to W steels being water quenched, most industry doesn't use the thin cross sections that knifemakers use. If you want to do water or brine, you REALLY run the risk of cracking, IMO. Precise temperature control makes cracking less likely, as Jank said. Warpage is part of the deal, whatever you use.

Normalizing is a way of making the grain smaller. If you've forged the blade, you've created large grain by repeatedly taking the steel up to forging temperature. Normalizing makes the grain smaller, which gives you much better steel performance after the quench. If you haven't forged, normalization becomes less important. I don't normalize blades that I grind from bar stock.

Air quenching steels are another animal altogether. IMO the best way to do air quenching steels is to plate quench between two plates of aluminum. It draws the heat faster than air alone, and it helps keep the blades from warping.

[Bucksaw]

I got ya. I haven't got any true quench oil, I usually use old motor oil for my sawblade knives, so that's all I have. Is there another kind of light oil that I can get to quench the 1090 and W1, besides the high dollar quenching oil? I don't normally use old files because most of them are too thick IMO, so I really don't want to spend a lot of money to buy something that I may not use more than a handful of times, ever.

[Bjankowski]

Bucksaw I normalize every blade regardless if its only stock removal. Grinding, filing, etc. all set up some stress in steel, and normalizing will relief stress and will reduce the element of grain growth.
I normalize three times before heat treat; depending on what steel I'm using I'll bring it to critical temp ( where you would normally quench) I hang it using holes in the tang to hang the blade so that there is not heat transference if I lay the blade down. Make sure you're in a dark environment, let the blade hang until all the color is completely gone, and repeat two more times. Then you can proceed with your heat treating.

Air quench is for alloys however; most air quenching is for larger parts and not applicable to blades.

[Bucksaw]

OK, so when normalizing, you don't allow it to cool completely to touch. This should help a lot with the saw steel as well, given the fact that most of them are work hardened and have gone through several heat cycles during service.

Thanks guys, you are being a great help. Im slowly getting a step-by-step pattern in my head of what needs to be done, how long, and how hot. If you think of anything else, don't hesitate to post it up.

[Bjankowski]

If your going to use oil throw that motor oil away and get some canola oil, motor oil fumes can cause cancer. Besides it smells better to smell fries cooking than an old junker beat up car. lol.

[Bucksaw]

That depends on whether you're a gear head or a fat kid. Luckily, I'm both.

[Txcity]

I don't think the type of oil matters much. If you find it does, I'd love to hear about it.
You're going to have a problem with cracking depending on your quench temperature. You may experiment with increasing the temperature of your quench in order to prevent cracking if you encounter it. I'm a little confused about what you're doing, so hopefully this will help, but if you're making saw blades, then you'll want a surface hardening technique. In this case, if you heat the surface with a torch, then quench, there's no chance of cracking since the center is cool and the outside it hot.
To prevent cracking, you may consider forming with no sharp interior corners...use a larger radius if you can.