O1 versus A2

[Richard Gillespie]

Did a search but must not have phrased it correctly. What are the strengths and draw backs on each heat treatment when it comes to blades for planes and maybe chisels?

[Jeff Hamilton Jr.]

In Mr. Hock's new book, "The Perfect Edge," he does a great job of describing the difference between the two steels. In simple terms (bcz I'm no expert!) The O1 or "oil-cooled" steel is finer and thus able to reach a sharper edge as a result.

The A2 "air-cooled (or quenched -- see, told you I wasn't an expert!) is more durable but has more chromium particles (I believe) so it will not take as fine an edge.

The question is, how much do you use the blade in question? I have a set of Lie Nielsen's chisels and have gotten them pretty sharp (for me). They are A2.

I own one of Mr. Hock's replacement blades for a Stanley #6 in O1 and it gets even sharper, I believe, and has stayed that way quite awhile. I'm am just a hobbyist though, so don't use them a whole lot.

Hope I was a little help . . .

[Richard Gillespie]

Thanks Jeff!

[David Weaver]

For plane blades, don't worry too much about the alloys yet unless you're sharpening with oilstones. If you use oilstones and your last step in your regimen is also an oil stone, then I'd go with O1.

For chisels, I would go with O1 with the exception being for mortise chisels. LN's little mortise chisels are A2 and they are really tough, but the bevel angles that O1 is better at are likely to be where you'll end up sharpening most of your chisels, especially if you like to pare or work with a fair amount of softwoods.

If you sharpen with sandpaper or waterstones or ceramic stones or diamonds, I think all of those cut the carbides in A2 steel fine. I have never had a lack of sharpness in A2 where you could ever see a difference in the surface of what you're planing - either will give you a mirror finish if you hone to an adequate grit.

Too much is made of the O1 vs. A2, especially if your sharpening setup handles both equally well. You're probably going to end up with a combination of them, anyway.

[Christian Castillo]

All steels, if properly sharpened with the correct sharpening media, achieve the same initial sharpness. From the charts that I have seen about edge retention, 01 drops its sharpness slower than A2 in the beginning, but then A2 settles and holds its sharpness while 01 continues to decline. What I take this to mean is pretty much what David recommends. For tasks where optimal sharpness is required, such as paring or finish planing, you will usually never really allow your edge to degrade to the point where A2 shines without re honing, so it makes more sense to use 01, which is easier to get back to it's initial sharpness and 01 will allow you to use lower bevel angles, which is good for paring. On the other hand, mortising, where near arm-shaving sharpness is good enough, it would be much better to have a steel that can hold a very sharp, but not super sharp edge for a very long time.

Of course the type of wood you work can easily change my summary, such as very hard or abrasive woods, where the toughness and superior abrasion resistance of A2 would make it shine even more. What you use to sharpen could change this as well, very fast water stones/diamond/hollow grinding/micro bevels could make sharpening A2 so easy, that their would literally be no difference in the time taken to sharpen 01. I guess what I'm saying is that you should chose the steel for the job based on what you have to sharpen with.

[george wilson]

It's oil HARDENING,and air HARDENING.

[Richard Gillespie]

Thanks to all who took time to reply. I gained some very valuable and useful information.