Grinding and Sharpening O1: Belt Recommendations & Technique

O1 is one of the easiest steels in the shop to work, and one of the easiest to ruin with heat. It arrives as precision ground flat stock — genuinely flat and square, so you can lay out and profile without any surface prep — and it grinds, files and hand-sands like a steel that wants to cooperate. The catch is the low temper: at 350 to 400°F, O1’s margin for a hot grind is thinner than almost anything else you will put on a 2×72.

Grinding Annealed O1

Annealed O1 cuts fast and predictably. Fresh 36 to 60 grit ceramic or zirconia belts move it quickly with light pressure, and it drills and files without complaint — which is exactly why it is such a good stock-removal steel for a first kiln-heat-treated knife. Because O1 needs a controlled 1475°F soak rather than a forge-and-magnet heat, plan to do most of your shaping before heat treat: leave the edge dime-thick, get the profile and plunges where you want them, and accept that post-heat-treat correction is slow work.

Grinding Hardened O1

At 59 to 61 HRC, O1 still grinds cooperatively — its carbides are fine and there is nothing in it that tears at a belt. Heat is the whole problem. Tempered at 350 to 400°F, the edge loses hardness the moment it goes past that, and a thin bevel on a hardened blade gets there startlingly fast. Keep the blade moving, dip constantly, use sharp belts rather than pressure, and slow the machine down for finishing passes — variable speed genuinely matters here (the case for it is in the 2×72 buyer’s guide). If you see straw colour appear, you have already gone too far.

Belt Progression

• Hogging (annealed): 36–60 grit ceramic — fresh belts, light pressure, let the grit do the work
• Bevel setting: 60–120 ceramic or zirconia
• Refinement: 220–400 — O1’s fine grain takes a clean 400-grit belt finish that hand sanding picks up easily
• Finishing: Trizact or structured abrasives, or straight to hand sanding — O1 polishes to a genuinely fine satin, and its lack of coarse carbide means no tear-out to chase

  

Full belt-selection logic in the Belt Buyer’s Guide.

Sharpening O1

O1 sharpens on anything. Its chromium and tungsten carbides are fine and sparse enough that ordinary aluminium-oxide and ceramic stones cut it cleanly — no diamond requirement like the vanadium-rich powder steels. It takes a very keen apex and strops back readily, which is a large part of why straight-razor and woodworking-tool makers have used it for a century. Run 15–17° per side for kitchen and slicing work, 20° for a hunter that sees bone. Method in How to Sharpen a Knife.

One habit worth building: O1 flash rusts on freshly ground steel, sometimes within the hour in a humid shop. Wipe and oil the blade after every grinding and sharpening session, or commit to a forced patina as a working finish.

Sources

• Knife Steel Nerds — O1 steel properties and heat treating
• Hudson Tool Steel — O1 technical data