I received this question in episode 3 of the Ask Brian Boggs Show:
A-2 steel and PMV-11 are relatively new steels on the market. Do you have a preference for alloys, or would you rather stick with the traditional O-1 steels?
I’ve done a lot of experimenting with steels, particularly when I was first started to make spoke chairs for sale. This was back in, I think late ’80s, early ’90s. I experimented with irons, custom made irons of F-5, A-2, A-11, W-2, M-4. I think, it was T-11, and different heat treating processes of some of those, and of course O-1. The differences were significant in some ways mostly in how easy they sharpened, or how well they responded to the stones I was using at the time, which were water stones for some things. But mostly, even then, I was using diamond compound. I think that there are very specific applications for each of these different types of steel.
The ones that are most popular now, the alloys most popular now, are the A-2 and PMV-11. The PMV-11 is a proprietary metal that, as far as I know, only Lee Valley Tools, and Veritas has offered through their planes, and possibly, some other tools. I only know of their planes using that. I haven’t used it personally. I’ve heard only great things about it. I have used A-2 steel a lot, and while it has been demonstrated to last, or to hold an edge, about six times longer than O-1 in wood working, it’s much more difficult to sharpen than O-1. I think, that if you’re not using diamond I don’t think you’re going to get a great edge with any of the alloys.
The O-1 is friendlier to pretty much any sharpening process. It holds an edge well enough that I wouldn’t bother with any of the alloys, unless you’re in production, your using a hand plane for hours on end. And you have the patience to develop the skills to sharpen it. If you are used to using O-1, and then you start using any kind of alloy, and you sharpen you’re O-1 steel, you’re probably not going to get great results. I’ve had to develop specific techniques for removing the burr, which is the biggest challenge when you go from O-1, which is a relatively brittle steel at it’s favorite hardness, which is around 62 Rockwell, maybe 60, 62, somewhere in there. If that hardness is a relatively brittle steel, which means, that when you’re sharpening it the edge breaks off, or is removed, rather than simply folding over.
Whereas, the tougher alloy steels, even at those harnesses, don’t shear as well on the stone. They tend to form a more tougher burr, a more flexible burr, which is a lot tricker to get rid of. The standard techniques for sharpening O-1 steel often don’t get rid of that burr. It will seem like a problem of the metal, but I think it is a problem more of the metal not being adapted to, or a sharpening process, not being adapted appropriately to the metal. There’s just so many variables that will impact whether, or not, one steel or the other is appropriate. But O-1 is a simplar steel to work with, and most people find it a favorite certainly over A-2. I cannot speak to PMV-11. I look forward to trying one of those steels sometime, one of those blades.