O1 vs A2
Two tool steels from the same era and the same shelf, separated mainly by how they harden. O1 quenches in oil and takes a keener edge; A2 hardens in still air, warps less, and is meaningfully tougher. The choice is usually settled by what the knife has to survive.
Quick Verdict
Pick A2 for hard-use blades and for flat, warp-free heat treatment — it is clearly the tougher steel. Pick O1 for slicing knives where a finer, keener edge matters, and when your heat treat setup tops out well below 1750°F.
Toughness
A2 wins, and it is not close. Its restrained carbide structure and lower effective carbon give it real impact resistance at working hardness, which is why it spent years as Bark River's hard-use steel. O1 is a slicer that will chip where A2 will deform.
Edge Retention
Roughly even in slicing life, with O1 taking the finer edge. A2's higher chromium gives more carbide volume and slightly more wear resistance; O1's finer carbides produce a keener apex that many makers prefer on kitchen and detail work. Neither threatens D2 or the powder steels.
Corrosion Resistance
A2 is marginally better at roughly 5% chromium versus O1's 0.5%, but the practical difference is small and neither is stainless. Both patina, both rust if neglected, both want oil.
Heat Treat
The deciding factor for most shops. O1 austenitizes at 1475°F and quenches in medium oil — reachable with a modest kiln. A2 needs 1750 to 1800°F with a 30 to 45 minute soak, but then hardens in still air or between aluminum plates, which means far less warp and no quench tank. If your oven cannot hold 1800°F, the decision is made for you.
Grinding
Both are cooperative by tool-steel standards. A2 hand-finishes exceptionally cleanly; O1 grinds a touch easier annealed and arrives as flat stock. Neither fights back the way D2 does.
Best-Use Scenarios
A2: camp knives, choppers, bushcraft blades and tough kitchen workhorses, plus plane irons. O1: kitchen knives, hunters, razors, folders and woodworking tools where edge fineness beats impact resistance.