Tool Steel Selection for Blanking and Piercing Dies
Blanking and piercing dies work under a combination of high compressive stress, sudden fracture release, and repeated edge contact with the work material. When the punch penetrates the sheet, the cutting edge is exposed to pressure, friction, localized heating, and impact at breakthrough. As a result, these tools usually fail in one of two ways: the edge wears progressively, or it chips and cracks under shock loading.
For this reason, tool steel selection for blanking and piercing dies is not a matter of choosing the hardest grade or the most wear-resistant grade. The real task is to match the steel to the dominant failure mode in production.
Core Selection Principle
The central selection problem in blanking and piercing dies is balancing wear resistance and toughness.
If wear resistance is too low, the edge loses sharpness quickly. Burrs increase, part dimensions drift, and regrinding frequency rises. If toughness is too low, the edge cannot tolerate breakthrough shock, and chipping or cracking begins long before normal wear life is reached.
This means the correct grade depends mainly on three production conditions: production volume, material thickness, and shock severity during cutting. High-volume, abrasive service pushes selection toward higher wear resistance. Thick stock, unstable loading, or severe breakthrough shock push selection toward higher toughness.
Selection of Common Tool Steels
AISI A2 Tool Steel | 1.2363 | SKD12
A2 is a balanced choice for blanking and piercing dies operating under moderate wear and shock. It offers better toughness than D2 and better wear resistance than shock-resisting steels such as S7. This makes it suitable for medium production runs in which the die must resist both edge wear and occasional impacts without becoming overly brittle.
A2 is often selected when the application does not clearly demand either maximum wear resistance or maximum shock resistance.
AISI D2 Tool Steel | 1.2379 | SKD11
D2 is used when abrasive wear is the primary cause of die failure. Its high carbide content gives it a strong edge retention, which is valuable in long production runs and in operations where maintaining cutting-edge geometry is critical.
However, D2 is less tolerant of breakthrough shock than A2 or S7. In blanking and piercing dies subjected to thick material, unstable press conditions, or high-impact loading, D2 is more likely to chip at the edge. It is therefore best suited to high-volume work where loading is relatively stable and wear control matters more than shock resistance.
AISI S7 Tool Steel | 1.2550
S7 is chosen when die failure is caused by impact rather than wear. Its main advantage is toughness. In heavy-duty piercing, thick stock applications, or cases where punches and die edges tend to crack unexpectedly, S7 is often the safer choice.
The trade-off is lower wear resistance. In other words, S7 usually lasts longer against breakage but not longer against abrasive edge wear. It is selected to prevent catastrophic failure, not to maximize edge life in abrasive service.
AISI O1 Tool Steel | 1.2510 | SKS3
O1 is a practical option for short- to medium-production runs where the loading level is not severe and the cost of tooling must be controlled. It provides sufficient wear resistance and adequate toughness for general blanking and piercing, but it is not the preferred solution for very high production volumes or severe shock conditions.
O1 is typically selected for economical tooling rather than for maximum die life under demanding service.
AISI M2 Tool Steel | 1.3343 | SKH51
M2 is used in more demanding blanking and piercing applications where high wear resistance must be combined with strong resistance to compressive loading. It is especially relevant in high-volume production or in thicker material, where conventional cold-work grades may lose edge performance too quickly.
Compared with D2, M2 can offer stronger support in applications where edge wear and heavy service both matter. Compared with S7, it is chosen when wear resistance remains a higher priority than shock resistance.
Practical Selection Logic
In practical terms, blanking and piercing die selection can be simplified as follows.
When the die fails primarily due to progressive edge wear, D2 or M2 is usually the better choice. When the die fails primarily due to chipping, cracking, or sudden breakage, S7 is a more suitable choice. When the application sits between these extremes, A2 is often the most balanced solution. When production demand is limited, and tooling economy is the main concern, O1 can still be a reasonable option.
This is the most useful way to select tool steel for blanking and piercing dies because it starts with actual failure behavior rather than abstract property comparisons.
Summary Table
| Tool Steel Grade | Typical Working Hardness | Main Selection Reason |
| A2 | 58–60 HRC | Balanced wear resistance and toughness for medium-duty blanking and piercing dies |
| D2 | 58–60 HRC | High wear resistance for long runs under relatively stable loading |
| S7 | 56–58 HRC | High toughness for severe shock, thick stock, or chipping-sensitive applications |
| O1 | 58–60 HRC | Economical choice for general or shorter-run tooling |
| M2 | 60–62 HRC | High wear resistance and compressive strength for demanding production conditions |
Conclusion
Tool steel selection for blanking and piercing dies should be based on how the die actually fails in service.
If the main problem is edge wear, the selection should move toward higher-wear-resistant grades. If the main problem is chipping or fracture, higher-toughness grades are more appropriate. Once this distinction is clear, the choice among A2, D2, S7, O1, and M2 becomes much more direct and technically justified.