Jon Siegel replies: I assume that by asking this question, you want to know what kind of steel to purchase to make your own cutting tools. It is important that you choose a steel that you can heat treat yourself with the equipment you have, (hardening and tempering).
That’s why I use W1 or O1 for the chisels I make. These can be heat treated with a torch (to 1440°F), do not require a furnace, do not require prolonged heating time, and can be quenched directly to room temperature. The entire heat treating process takes only a few minutes. For more information see my article in the April 2007 issue of The Old Saw — Woodturning Chisels You Can Make.
Garrett Hack replies: O1 is a common high carbon tool steel, similar to what you might find in an old chisel or plane iron. A2 is a steel alloy increasingly used in high-end planes and chisels such as by Lie-Nielsen and Lee Valley. A2 is tougher than O1, so an edge lasts longer with the trade off of some chipping. A2 is typically cryogenically treated, and yes, it makes a difference. Supercooling contracts the steel into a more dense structure, creating a more durable edge. No one steel can do it all. I like a high carbon steel for my smoothing planes because it takes a keener edge and resharpens so easily. A2 holds its sharpness longer, especially against abrasive woods and other materials, but it takes more time to sharpen.