O-1 vs. A-2

I'll throw in a third option. A number of years ago, I asked Kevin Cashen what steels he would recommend for say a reasonably priced "mid tech" line using readily available carbon steels. His recommendations were O1 for blades under 5 inches and 52100 for larger blades.
 
Am I wrong to say that O1 can take a slightly more keen edge and would be easier to sharpen? Might be ever so slight that it’s not noticeable to most..?
 
Don't know about that. More likely, you would say that O1 would be a tad more abrasion resistant that lower temp austenized 52100 at the expense of some toughness. 52100 done at 1475F gets as fine of an edge as any steel out there, hence its use in high end kitchen knives.
KNelson said:
Am I wrong to say that O1 can take a slightly more keen edge and would be easier to sharpen? Might be ever so slight that it’s not noticeable to most..?
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jdm61 said:
Don't know about that. More likely, you would say that O1 would be a tad more abrasion resistant that lower temp austenized 52100 at the expense of some toughness. 52100 done at 1475F gets as fine of an edge as any steel out there, hence its use in high end kitchen knives.
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I've been curious about 52100 vs O1 for a while. My favorite steel is 1095 I guess because I hand forge and like hamons.
That said I've used 52100 for good performance kitchen knives and have been wondering if O1 would hold an edge longer. It looks better on paper imo.
That said I do my 52100 at 1500-1525 into parks50 using a drum forge. Ive never gotten it above 65Hrc quenching from 1475 before, 1500-1525 range I can always get max hardness. RA is never an issue...
-Trey
 
I would pick A2 but it takes more to get out of it in the heat treat, including using stainless steel foil and subzero freeze.

But O1 is just so simple to work with. I made a camp knife out of O1 over 10 years ago, when I first started making knives, and it held up perfectly well over the years chopping down tree branches for firewood and other camping tasks. Rarely needed sharpening. I forgot what I used for the heat treat. This week when I measured the hardness I found out it was at 66 rc! I love steels that can hold up at high hardness without being chippy. A2 would require cyro to acheive the same performance, but is more wear resistant and has a mild touch of corrosion resistance which protects your edges from rusting. 52100 is essentially indistinguishable from O1, is a bit more alloyed. It's between O1 and A2, but closer to O1.

Now I use 1095 as it is half the price of O1 and quality seems to be good (properly annealed, ground flat, no scale, no inclusions). I found oil quench works just fine for 1095 if I keep the knife thin. Getting full hardness.
 
The main A2 I have has been from LT Wright and it is a bit more difficult to sharpen but holds it's edge better also ... so always a trade of from one steel to another.
 
I have some woodworking hand planes with A2 and or O1 irons.
Don't have any data to base this on, but I seem to get the O1 irons a little more scary sharp than my A2 irons.
O1 might be a little easier to reprofile when the edge is damaged, too.
This is just how it seems to me.
Perhaps I'm doing something wrong with my A2 honing process, but after a few decades of sharpening my own tools I have become consistent with my methods.
I can just get some steels sharper than others.
A2 gets ridiculously sharp. Nothing wrong with A2.
 
Probably has to do with carbide size at the edge. O1 likely has smaller carbides, which will equate to a finer/sharper edge.
 
IF you have access to an electric kiln, A2 is much easier to heat-treat, IMO. Wrap in foil, quench packet between aluminum plates. IIRC, the results of subzero with A2 were inconclusive or minor on Larrin's site. (but would suffer correction if wrong...) And is is quite stable in heat-treat.

O1 should ALSO be soaked in an electric kiln for best performance, but then you have to deal with oil. Which should be a proper quench oil, not canola like 1084. Bleh. If I'm going to use a kiln and foil, I'd rather not wrestle a hot blade out of foil to quench in oil - or dunk in-packet either. Maye if you have a gas-purged kiln it's a negligible difference.

A2 is only harder to sharpen by hand if you're not using diamond plates. If you're going to step beyond O1 in any direction, diamond plates are necessary for hand-sharpening. Then the difference in sharpening is minor.

A2 is easily made sharp enough by hand to whittle hair.

Don't get me wrong, I like using O1 blades, but between my other chosen carbon steels as a maker (1084 and A2), it has the disadvantages of both in heat-treat, and doesn't out-perform either in enough categories to make the heat-treat trouble worth it.
 
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