A2 Vs O1

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kelsil

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Jun 8, 2011
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Hi everyone. I'm trying to fish for some words of wisdom regarding this two types of steel. For edge holding ability, wear resistnace and toughness, which between the two is best for very thin(about 1/16"
thick) small blades? Thanks.
 
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01 makes a good blade as does A2. When people like Randall chooses 01 and Phil Hartsfield chooses A2 it is because they both make excellent blades.

Either one you choose will serve you well
 
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There is some discussion in the woodworking world that A2 has larger carbides than O1, so might not have the edge retention of O1 for thinner blades. I haven't seen this formally tested, so it might just be theory at this point.

I know the question was about the end results, so this reply is a little off topic:

I found A2 much easier to heat treat successfully than O1.

Both need to be held at temperature for a few minutes, so both essentially require a controlled temperature heat treat (for most, that's an electric kiln, although there are also salts, and some folk have very cool solutions with thermocouplers in muffled forges).

The quench is the difference: unless you are in a reducing atmosphere, both steels need to be protected from decarburization. If you are using stainless foil, optimal results require quick work to get the O1 out of the foil packet, into the oil, and cooled off most of the way. A2, on the other hand, can be quenched between plates, or pulled out of the foil and put into oil at a more leisurely pace. Further, there is no need with A2 to pursue a fast quenching oil - pretty much anything as fast or faster than blown air will work well.
 
Just my $.02

I changed from O1 to A2 recently for carbon steel; it seems that the edge last much longer in testing. I was very happy with my O1 results I just dislike the oil quench mess/smell.
 
I have used both and very happy, with a thin blade I like A2 since I can use a plate quench and keep it flat with little trouble. Also there is no decarb so with a thin blade you can take it near finish and then just clean up after HT. I made drop point hunters with both and tested side by side, I did not see any real difference, not real scientific but both performed really well. The other reason I like A2 these is a little bit of corrosion resistance, I have had O1 get rust spots when I let it on the bench, probably from dew.
 
lazlo said:
I thought O1 had better wear resistance, and A2 had better toughness?
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You've got it backwards. I don't care what the charts say. O-1 is a bit tougher than A-2, but A-2 has better wear resistance.
 
kelsil said:
...best for very thin(about 1/16"
thick) small blades? Thanks.
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You are wise to specify the size blades you want to make, it's very important to steel selection.

I presume you will be using such thin blades for precise cutting, not heavy chopping. So the differences in toughness between A2 and O1 aren't that big of a concern in this case. Personally, I would choose A2 simply because it should hold an edge a bit longer. O1 should be a little easier to sharpen.

As said above, A2 (while not "stainless" by any means) should have somewhat better corrosion-resistance, too. But honestly either should work very well for a thin cutter/slicer as long as they're properly heat-treated.
 
Thank you all for the great responses. They're very much appreciated. I have a follow up question if you guys don't mind. When heating to harden this thin small blades(~1/16"thick x 1/2"wide x 4-5" long), what would be the best SOAKING time? Because of their size, I'm sure that they can reach the required temperature very much quicker than thicker and bigger blades. I'm just wondering if required soaking is the same regardless of the size of the blades to be tempered. Thanks again.
 
I have done 1/16 A2 and I still give it 20 -30 minutes, probably does not need that long but the oven is on autopilot. How are you planning on heating, electic oven? gas forge?
 
Patrickknives said:
I have done 1/16 A2 and I still give it 20 -30 minutes, probably does not need that long but the oven is on autopilot. How are you planning on heating, electic oven? gas forge?
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Am planning to buy an elec. oven. I've been using a simple propane gas forge but looks like the right soaking time at the right temp is a must for a sound HT, specially with the more complex steels. Thanks.
 
Don Hanson III said:
They both have too much alloy for me... Just sayin.
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Are you implying that some simple steels would match or equal O1 & A2 with regard to wear resistance and toughness? If so, would you mind saying/mentioning them too also?:confused: Thanks Don.
 
I think Don's referring to the fact that they're deep hardening steels, and you can't create much of a hamon.
 
same idea as Troop said...

thats obviously a chart from crucible service... look at how good the cpm steels are.. wow ... why would you concider any thing else ...

carbon steels rule !!!

Troop said:
You've got it backwards. I don't care what the charts say. O-1 is a bit tougher than A-2, but A-2 has better wear resistance.
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kelsil said:
Are you implying that some simple steels would match or equal O1 & A2 with regard to wear resistance and toughness? If so, would you mind saying/mentioning them too also?:confused: Thanks Don.
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Don is referring to his own special melt of W-2. I have a small supply of it, but I'm saving it for a special occasion.:)
 
lazlo said:
I think Don's referring to the fact that they're deep hardening steels, and you can't create much of a hamon.
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Yeah, perhaps. But I think there may be more to it than that. The alloys and the carbides do a lot of great things for steel, but the perfectly homogenous simple steel has (in my opinion) the best potential for fine edge stability. Generally speaking, a simple steel gets sharper easier than a complex steel, and will tolerate more nonabrasive abuse. The best fine edge stability I have personally ever observed was in a W2 blade (just a pinch of vanadium for grain refinement). I don't think there is a knife out there that will chop a 2X4 in half and still tree top hair, but if there were, I wouldn't be surprised if it were W2.
 
Nathan the Machinist said:
Yeah, perhaps. But I think there may be more to it than that. The alloys and the carbides do a lot of great things for steel, but the perfectly homogenous simple steel has (in my opinion) the best potential for fine edge stability. Generally speaking, a simple steel gets sharper easier than a complex steel, and will tolerate more nonabrasive abuse. The best fine edge stability I have personally ever observed was in a W2 blade (just a pinch of vanadium for grain refinement). I don't think there is a knife out there that will chop a 2X4 in half and still tree top hair, but if there were, I wouldn't be surprised if it were W2.
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Yep... Very Well said Nathan!

The hamon thing is just gravy. :)
 
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