Selection of Tool Steel for Fine Blanking Dies
Fine blanking is a precision cold forming process designed to produce fully sheared edges with minimal fracture zones. By applying a V-ring indenter, the material is subjected to high compressive stress before shearing, thereby promoting plastic flow rather than crack propagation.
Compared with conventional blanking, this results in significantly higher contact pressure, tighter clearances (typically around 1% of sheet thickness), and severe friction at the cutting interface. At the same time, punches must withstand strong stripping and ejection forces.
Under these conditions, tool failure is primarily driven by abrasive wear, adhesive wear (galling), and edge chipping due to stress concentrations. Tool steel selection, therefore, directly determines edge stability and die life.
Selection Factors
The key challenge in fine blanking is maintaining edge integrity under simultaneous wear and extreme compressive stress.
High hardness is required to resist wear and hold tight clearances. However, increasing hardness reduces toughness, making the cutting edge more prone to chipping under load. In fine blanking, once microcracks initiate at the edge, they propagate rapidly, leading to premature failure.
For this reason, the steel must provide enough toughness to absorb localized overload while maintaining sufficient wear resistance to prevent rapid edge degradation.
Friction at the cutting interface further complicates selection. High contact pressure promotes material adhesion to the punch surface, especially in long production runs. This increases the risk of galling and accelerates wear. In practice, steels with poor microstructural uniformity are more prone to crack initiation and unstable wear behavior.
As a result, tool life depends on the balance between carbide-driven wear resistance and matrix toughness, rather than hardness alone.
Recommended Tool Steels
In fine blanking, different components of the die set require different material properties. Selection should be based on function rather than on a single grade throughout.
AISI A2 Tool Steel | 1.2363 | SKD12
A2 is typically used for V-ring plates, punch holders, and other structural components where resistance to cracking is critical.
It offers better toughness than high-carbon high-chromium steels, allowing it to withstand combined compressive and stripping forces without brittle failure. Its dimensional stability during heat treatment also helps maintain die alignment and clearance control.
A2 is generally applied at 57–60 HRC and is suitable for moderate production volumes or applications where chipping risk is a concern.
AISI D2 Tool Steel | 1.2379 | SKD11
D2 is the standard choice for cutting edges in high-volume fine-blanking operations where wear resistance is the limiting factor in tool life.
Its high carbide content provides excellent resistance to abrasive wear, allowing the die to maintain sharp edges and tight clearances over long runs. However, its lower toughness makes it more sensitive to edge chipping under unstable loading conditions.
D2 performs best in stable processes with controlled impact and is typically used at 58–62 HRC.
AISI S7 Tool Steel Supplier | DIN 1.2355
S7 is used for heavily loaded structural components such as pressure plates and retainers. These parts absorb significant compressive and impact forces during operation.
Its high impact toughness prevents cracking under repeated loading, making it reliable in high-stress support roles. However, due to its lower wear resistance, it is not suitable for cutting edges.
S7 is typically heat-treated to 54–58 HRC to maximize toughness.
PM (Powder Metallurgy) High-Speed Steels
PM high-speed steels are used in demanding fine blanking applications where both wear resistance and toughness are required simultaneously.
Their uniform microstructure reduces the number of crack initiation sites compared with conventional D2, significantly lowering the risk of edge chipping. At the same time, they maintain high hardness and wear resistance, making them suitable for high-load and high-precision operations.
These steels are typically used at hardness levels above 60 HRC when extended tool life and process stability are critical.
Summary Table
| Tool Steel Grade | Typical Hardness | Main Advantage for Fine Blanking Dies |
| AISI A2 | 57–60 HRC | Better toughness; suitable for structural parts and moderate loads |
| AISI D2 | 58–62 HRC | High wear resistance; ideal for long production runs |
| AISI S7 | 54–58 HRC | High impact resistance; used for support components |
| PM High-Speed | 60–64+ HRC | Combines wear resistance and toughness; reduces chipping risk |