Choosing the correct hardness for a die-making blade is crucial to ensure optimal performance, longevity, and cost‑effectiveness. The hardness affects wear resistance (resistance to material loss), toughness (energy absorption without fracturing), and the blade’s ability to withstand cutting forces. Here’s a step‑by‑step guide to selecting the right hardness:
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Soft Materials (e.g., rubber, foam, soft plastics):
A lower hardness (e.g., HRC 50–55) may suffice since wear resistance is less critical.
Medium‑Hard Materials (e.g., cardboard, leather, some plastics):
Moderate hardness (HRC 55–60) balances wear resistance and toughness.
Hard Materials (e.g., metals, composites, hard plastics):
Higher hardness (HRC 60–65+) is needed for wear resistance but must be balanced with toughness to prevent chipping.
Soft Materials | Medium‑Hard Materials |
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Shearing blades (e.g., for steel‑rule dies) need higher hardness (HRC 60–65) to maintain a sharp edge.
Punching dies may require slightly lower hardness (HRC 58–62) to absorb impact without cracking.
High‑Speed Cutting (e.g., rotary dies):
Higher hardness (HRC 62+) is preferred to resist wear from friction.
D2 (high‑carbon, high‑chromium): HRC 58–62 (excellent wear resistance).
A2 (air‑hardening): HRC 58–60 (good toughness).
O1 (oil‑hardening): HRC 58–61 (balanced properties).
Carbide (tungsten or ceramic):
Extreme hardness (HRC 70+) for ultra‑wear‑resistant applications (e.g., abrasive materials).
Higher hardness = better wear resistance, but lower toughness (risk of chipping).
Lower hardness = better impact resistance, but faster wear.
Solution: For abrasive but brittle materials, use a slightly lower hardness with a tougher steel grade.
Consult blade suppliers (e.g., Böhler, Uddeholm, Mitsubishi) for their recommended hardness based on your application.
Standard industrial die blades often range between HRC 58–62.
Start with a mid‑range hardness (e.g., HRC 60) and test performance.
Adjust based on:
Edge retention (too soft → rapid dulling).
Chipping/cracking (too hard → brittle failure).
| Application | Recommended Hardness (HRC) | Material Example |
|---|---|---|
| Soft non‑wovens, foam | 50–55 | Rubber, EVA foam |
| Cardboard, leather | 55–60 | Paperboard, textiles |
| Plastics, thin metals | 58–62 | PET, aluminum foil |
| Sheet-metal stamping | 60–65 | Steel, stainless steel |
| Abrasive composites | 62+ (or carbide) | Fiberglass, carbon fibre |
If unsure, consult a tooling engineer or blade supplier to match hardness with your specific material, cutting speed, and die design. Proper heat treatment and coating (e.g., TiN, CrN) can further enhance performance.
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