Steel grades for machine knives: what each one is for
Most blade problems are not grinding problems. They are the wrong steel for the job, chosen because that is what the last supplier stocked. This is the short list of grades we actually grind, what each one is good at, and the case where it is the wrong answer.
The grades, side by side
| Grade | Chinese designation | Hardness | Used for | Do not choose it when |
|---|---|---|---|---|
| T1 | W18Cr4V | HRC 62–64 | Paper guillotine knives, long sheeter knives, high-volume printing | The stock is recycled or contaminated — it chips where M2 bends |
| M2 | W6Mo5Cr4V2 | HRC 60–64 | Paper knives on mixed stock, veneer slicer knives, HSS inlay edges | You need the last 5% of wear resistance on clean coated paper |
| 6CrW2Si | 6CrW2Si | HRC 55–58 | Veneer peeling knives, chipper knives, long woodworking blades | The log is heavily contaminated with sand or grit |
| 9CrSi | 9CrSi | HRC 55–59 | Veneer pressure bars, chipper knives, shear blades for thin sheet | You need maximum edge holding on abrasive board |
| 5CrW2Si | 5CrW2Si | HRC 53–57 | Shearing machine blades, metal-cutting straight blades | The machine cuts paper — too soft, dulls in hours |
| HSS inlay | BF / inlay | HRC 60–64 at the edge | Veneer slicer knives, long knives that need a tough body and a hard edge | The blade is short enough to make solid HSS economic |
| Stainless (food grade) | to your grade | HRC 54–58 | Fish and food slicing blades, wet or salted product | There is no corrosion requirement — carbon steel holds an edge longer for less |
Hardness is a trade, not a score
Every point of hardness buys wear resistance and costs toughness. On paper, that trade is almost free — the load is gentle and predictable, so HRC 62–64 is safe. On wood, the load is not predictable: a knot, a staple, a frozen log. That is why peeling knives run at HRC 55–58 even though harder steel would wear more slowly.
The diagnostic is how your current blades fail:
- Wears evenly, edge stays smooth — abrasion. Go harder, or go to a more wear-resistant grade.
- Small chips along the edge, no pattern — impact or contamination. Go softer, or increase the edge angle.
- Edge rolls over and stays bent — too soft for the load. Go harder.
- Cracks running back from the edge — too hard or badly heat treated. Change grade, not supplier.
What the grade does not fix
Three problems look like steel problems and are not:
| Uneven veneer thickness | Pressure bar gap, knife parallelism or lathe alignment. A harder knife will produce the same wavy sheet, more slowly. |
| Fuzzy cut on the bottom sheets | Cutting stick worn, blade depth wrong, or clamp pressure low. Replace the stick before ordering a new knife. |
| Blade dulls in days | Check what is in the material first: grit on logs, staples in recycled paper, filler in board. No grade survives sand. |
How to specify a knife in one email
Send four lines: the machine model, the size of the old blade, what you cut, and how the old blade failed. Those four answers decide the grade without a conversation about price. If you already know the grade you want, say so and we grind to it — we will only argue if the choice contradicts what you told us about the failure.
Frequently asked
What steel are machine knives made of?
Most industrial machine knives are made from high speed steel (T1/W18Cr4V, M2/W6Mo5Cr4V2), shock-resisting tool steel (5CrW2Si, 6CrW2Si, 9CrSi) or, for food contact, stainless steel. The choice follows the load: abrasion pushes you to high speed steel, impact pushes you to shock-resisting steel.
Is harder always better for a machine knife?
No. Hardness buys wear resistance and costs toughness. A paper knife at HRC 62–64 is right; the same hardness in a veneer peeling knife would chip on the first knot. Match the hardness to the failure mode you actually see.
What does 6CrW2Si mean?
It is a Chinese standard shock-resisting tool steel: about 0.6% carbon, chromium and tungsten added for hardenability and wear resistance, silicon for toughness. It hardens to HRC 55–58 and is the default for veneer peeling knives and chipper knives in China.
T1 or M2 for paper?
T1 holds an edge longer on clean coated stock; M2 survives nicks better on recycled and heavily filled paper. There is a full comparison in T1 vs M2 for paper guillotine knives.
Can you supply the steel certificate?
Yes. Mill certificates for the heat are available with the shipment on request, and hardness is checked per batch.
Ask which grade fits your machine
Related reading: T1 vs M2 · Guillotine knife vs shear blade · What drives blade price · All technical guides →