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I am a novice knife maker and new member of ABS. I have a blade I've just ground out of 01 steel and would like some advise on heat treating. I have an acetylene torch. I also have a gas forge and quench 70 oil. Please advise.

Philip, O-1 is an excellent steel for knives that will see a lot of slicing and cutting, such as kitchen knives, hunters, skinners etc… I have worked with it for many years and have tamed a few of its quirks. While it is very easy to quench, and your chosen oil will do fine, it is not as easy as other steels to get the maximum potential out of it using just a forge. First I would strongly suggest setting your torch aside to save it for brazing and soldering operations, especially with O-1. If your blade is all stock removal, and the steel has seen no thermal treatments beyond what was done by the mill, it will be trickier to heat treat with your forge, but it can be done.

With alloying such as Cr, W or V, O-1 has the ability to hold carbon in carbide form very well. There are two ways to have your carbon- bonded into a carbide and unavailable during the heat treatment, or free and available to use to get maximum hardness. From the mill the steel will have as much carbon locked up in carbide as possible in order to facilitate free machining. This is not a problem for most industry since they will have controlled ovens which will allow them to soak the steel at a precise temperature long enough to unlock that carbon. You will not have that luxury with a forge, and certainly not with a torch.

You could heat treat it with the forge as is, and probably get a decent knife from it, but if you really nail the heat treat O-1 will really kick butt in the edge holding category. Thus if you are not getting its full potential, you are paying around 3 times the price of a simpler steel but not getting your money’s worth. If you had forged the blade the carbon is rearranged a bit and my respond a little better with the forge. What you could also do is a pre-heat treatment and do some rearranging anyhow. One good normalizing heat could be helpful. Heat it a bit warmer than you would for quenching, well above non-magnetic, and then allow it to air cool until the magnet sticks again (around 800F). You can then immediately proceed with your normal heating and quenching. This will help dissolve the carbides and put your carbon in a more ready to use form.

Or you could just proceed as is, I would guess it will be the difference of around 62HRC versus 65HRC as-quenched. The are many who will tell you that I am overthinking this, and that you could proceed without my input or with your torch, and do “just fine.” But when I give heat treating advice I always assume that the guy asking is shooting for the very best he can do, and I gear my answers accordingly. "just fine" or "good enough" will literally keep me awake at night, that is just the way I am wired and can't do it any other way.

I have a page at my website for working O-1, and many other steels, here is the page if it can be of help.

http://www.cashenblades.com/steel/o1.html

Kevin,

I have heard people say that O-1 is an air hardening steel. All of my books and the company I get mine from all say it is an oil hardening steel. Am I misunderstanding something? O-1 is the only steel I am working right now simply because it is the easiest for me to obtain, but I do want to achieve as much of it's potential in a knife as I can. Thank you for your time.

Kevin, I recently have purchased a Paragon heat treating oven. There were no knife holders with the oven so I've ordered those from Jantz. So now that I have a heat treating oven and I have several 01 blades that I'm working with, what is your advise on normalizing and heat treating using this oven? Thank you for your previous response. It was very informative. Thanks for your link to your website. It is very helpful.

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Kevin,

I have heard people say that O-1 is an air hardening steel. All of my books and the company I get mine from all say it is an oil hardening steel. Am I misunderstanding something? O-1 is the only steel I am working right now simply because it is the easiest for me to obtain, but I do want to achieve as much of it's potential in a knife as I can. Thank you for your time.

It is definitely oil hardening. A true air hardening steel will form complete martensite when cooled in still air. When cooled in the air O-1 will make lots or really fine pearlite and mixed bainites, perhaps with very thin sections a small smattering of martensite here or there, just enough of a mess to make cutting, filing and machining really miserable, but not enough to make anything you want hardened reliable.

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Kevin, I recently have purchased a Paragon heat treating oven. There were no knife holders with the oven so I've ordered those from Jantz. So now that I have a heat treating oven and I have several 01 blades that I'm working with, what is your advise on normalizing and heat treating using this oven? Thank you for your previous response. It was very informative. Thanks for your link to your website. It is very helpful.

The oven will permit you the longer soak at temp so the normalization may not be necesarry before to assist the hardening, but you can certainly use the same oven to do a normalizing should you start forging the O-1.

Thanks for the info. iam going to heat treat using the oven and soak for 5 min. then quench. we will see what happens hopefully. then temper at 425 for 1 hour twice.

Bruce

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Thanks for the info. iam going to heat treat using the oven and soak for 5 min. then quench. we will see what happens hopefully. then temper at 425 for 1 hour twice.

Bruce

I would bump that up to at least 8 minutes, if the steel is in the mill annealed condition.

I use a lot of O1 for my stock removal knives...Kitchen, hunters, and tactial. I harden at 1500 degrees and soak for 30 minutes then quench in oil prejheated to 120 degrees. (Chevron now but it is the old Texaco oil and I can't remember the number off the top of my head. Very quickly I go back in the furnace, Everheat, and draw at 500 degrees for 4 hours. I let the blanks cool in the oven until I can handle bare handed. This results in a hardness of 57-58 Rc. I also draw the spines and tangs back to a blue gray color with the cutting edge in a water bath. You can try lower draw temps if you want the material harder.