Free Sheet Metal Blanking & Piercing Tonnage Tool
Calculate stamping press tonnage ($F = P \cdot t \cdot \tau$), die shear angle force reductions, stripping force, and machine capacity safety margins.
⚙️ Cut Geometry & Material Properties
📊 Required Tonnage & Stripping Force
Recommended Tools & Equipment
Tested hardware and components for high reliability
Sheet Metal Blanking & Piercing Force Mechanics
Blanking and piercing operations shear metal between a hardened punch and die. The required cutting tonnage is directly proportional to the sheared cross-sectional area and the ultimate shear strength ($\tau$) of the alloy: $$F = P \times t \times \tau$$ Where $P$ is the total perimeter of the cutout, $t$ is the sheet metal stock thickness, and $\tau \approx 0.70 \times \text{Tensile Ultimate Strength } (S_{ut})$.
Reducing Tonnage with Die Shear Angles
When flat punches strike the sheet, the entire perimeter shears simultaneously, creating a sharp tonnage spike and loud snap-through vibration. Grinding a shear angle (beveled edge or rooftop shear) on the punch face causes the cut to occur progressively like a pair of scissors, reducing peak cutting force by 30% to 50% without changing total energy.
Stripping Force Requirements
As the punch penetrates the sheet, elastic springback causes the metal around the hole to grip tightly onto the punch body. Spring-loaded or polyurethane stripper plates must exert a stripping force equal to approximately 5% to 10% of the peak cutting tonnage to cleanly extract the punch without jamming.
Frequently Asked Questions
What is the difference between blanking and piercing?
In piercing (punching), the slug punched out is scrap and the surrounding sheet is the finished part. In blanking, the punched-out piece is the useful finished part and the outer strip is scrap.
How does punch-to-die clearance affect cutting tonnage?
Proper clearance (typically 8% to 12% of material thickness per side) allows upper and lower micro-cracks to meet cleanly in the shear zone, minimizing burrs and keeping cutting force at minimum. Insufficient clearance forces secondary shearing, dramatically increasing tonnage and accelerating punch wear.
How do I convert between metric kN and US tons?
1 US Short Ton = 2,000 lbs force = 8.896 kN. Conversely, 1 kN = 0.1124 US Tons. Stamping presses in North America are rated in US tons, while European and Asian presses are rated in metric tonnes (1 tonne = 9.807 kN).