Tooling & Stamping Prepress
Updated August 2026
Sheet Metal Stamping & Blanking Die Clearance Calculator
Calculate punch-to-die cutting clearance per side ($c$), total diametral clearance ($2c$), hole piercing vs part blanking tooling dimensions, punch shear tonnage ($F$), stripping force, and edge fracture profile for progressive and compound stamping dies.
1. Material & Stamping Setup
0.059 in (16 Gauge)
Hole diameter or blank outside size.
In piercing, punch diameter determines finished hole dimension.
π × D for round hole (e.g. 3.1416 × 25 = 78.5 mm).
2. Die Tooling & Tonnage Calculations
Clearance % per Side
8.0 % of t
Clearance per Side ($c$)
0.120 mm (4.7 mil)
Total Diametral Clearance ($2c$)
0.240 mm (9.4 mil)
Tooling Manufacturing Dimensions
Punch Size (Upper Tool):
25.000 mm
Die Opening (Lower Matrix):
25.240 mm
Punching Force ($F$):
36.5 kN (3.7 Metric Tons)
Stripping Force ($F_{strip}$):
3.7 kN (0.37 Tons)
Recommended Press Tonnage (+30%):
4.8 Metric Tons
Sheared Edge Profile & Die Clearance Cross-Section
Preparing Vector DXF Geometry for Stamping Die Tooling?
Progressive stamping dies and CNC punching stations require precise, closed-contour vector DXF geometry with verified corner relief radii to avoid stress cracks during heat treatment. SpotItLive converts raster part scans, drawings, and customer blueprints into clean, CAM-ready DXF and SVG geometry.
Vectorize Stamping Geometry Now →Stamping Clearance Percentage & Shear Resistance Guide
Standard engineering punch-to-die clearances per side as a percentage of stock thickness ($t$).
| Material Group | Tensile Strength | Shear Strength (τ) | Recommended Clearance per side (% t) | Edge Fracture Zone |
|---|---|---|---|---|
| Mild Steel (1008 - 1018) | 380 - 450 MPa | 300 - 340 MPa | 7% - 9% | ~ 65% Break, 35% Burnish |
| Stainless Steel (304, 316) | 550 - 700 MPa | 450 - 520 MPa | 9% - 11% | ~ 60% Break, 40% Burnish |
| High Strength Steel (DP600) | 600 - 750 MPa | 500 - 580 MPa | 10% - 13% | ~ 70% Break, 30% Burnish |
| Soft Aluminum (1100, 3003) | 110 - 150 MPa | 80 - 120 MPa | 4% - 6% | ~ 50% Break, 50% Burnish |
| Structural Aluminum (6061-T6) | 310 - 350 MPa | 200 - 240 MPa | 6% - 8% | ~ 65% Break, 35% Burnish |
| Cartridge Brass (C260) | 320 - 400 MPa | 240 - 280 MPa | 6% - 8% | ~ 55% Break, 45% Burnish |
| Copper (C110 ETP) | 220 - 280 MPa | 180 - 220 MPa | 5% - 7% | ~ 50% Break, 50% Burnish |
Key DXF Prepress Rules for Progressive Stamping Dies
- Hole-to-Edge Minimum Distance: Maintain at least $1.5 \times t$ (thickness) between hole edges and outer blank boundaries to avoid wall bulging.
- Internal Corner Radii: Sharp internal 90° corners on punches create severe stress concentrations leading to fatigue chipping. Incorporate minimum corner radii ($R \ge 0.5 \times t$).
- Slug Shedding Geometry: Add vacuum relief holes or spring-loaded ejector pin holes in the punch face for high-speed automated progressive dies.
- Clearance Allocation: Remember the universal rule: Punch determines hole size; Die determines blank size.