Metal Stamping Tolerance Guide
High-volume precision at production speed
Metal stamping is a high-speed, high-volume process where dies hit metal thousands of times per hour. Tolerances are driven by die quality, press accuracy, and material properties. Understanding what's achievable helps you design stamped parts that meet requirements without unnecessary die complexity.
Overview
Progressive die stamping holds ±0.05–0.10 mm on blanked features consistently across millions of parts. Formed features (bends, draws) have wider tolerances similar to sheet metal bending. Die quality and maintenance are the biggest factors in long-term tolerance consistency.
Tolerance Specifications
| Feature | Standard | Precision | Notes |
|---|---|---|---|
| Blanked Dimensions | ±0.10 mm | ±0.05 mm | Depends on material thickness and hardness. Thin materials (< 1.0 mm) hold tighter. |
| Hole Diameter (Punched) | ±0.05 mm | ±0.025 mm | Precision requires carbide punches and close die clearance. |
| Hole Position | ±0.08 mm | ±0.03 mm | Within a single station — across stations adds feed tolerance. |
| Bend Angle | ±1.0° | ±0.5° | Springback compensation built into die. Material lot variation affects angle. |
| Draw Depth | ±0.15 mm | ±0.08 mm | Deep draws are harder to control. Stepped draws improve consistency. |
| Flatness | 0.1 mm per 25 mm | 0.05 mm per 25 mm | Coining or planishing operations improve flatness. Adds die stations. |
| Burr Height | < 10% of material thickness | < 5% of material thickness | Burr side is predictable (toward die clearance). Specify burr direction if functional. |
| Material Thickness | ±10% of nominal | ±5% of nominal | Controlled by coil supplier. Specify incoming material spec if critical. |
Key Considerations
Volume = Precision
Progressive dies justify higher tooling cost but deliver tighter tolerances at high speed. For 50K+ parts, progressive stamping beats laser + brake forming.
Design for Progressive Die
Arrange features so they can be punched and formed in sequence. Avoid features that require the strip to be flipped.
Pilot Holes for Registration
Include pilot holes in your design (can be in scrap areas). They ensure precise strip positioning between stations.
Specify Burr Direction
Burr forms on the die clearance side. If burr direction matters for assembly or safety, call it out on the drawing.
💰 Cost Impact of Tolerances
Precision stamping requires carbide tooling, tighter die clearances, and more die stations — tooling cost rises 30–50%. Piece price barely changes since it's still high-speed.
Standard tolerances are achievable with tool steel dies and normal clearances. Very cost-effective at volume.
Invest in the die, not the piece price. A well-built progressive die holds tolerance over millions of hits. Cheap dies need frequent maintenance and produce inconsistent parts.
⚠️ Common Tolerance Mistakes
- ⚠ Designing features too close to bends — punched holes deform if closer than 1.5× material thickness to a bend line.
- ⚠ Ignoring grain direction — bending perpendicular to rolling direction gives best results. Specify grain direction for critical bends.
- ⚠ Over-tolerancing non-functional blanked edges — often only mating edges and hole positions need tight specs.
- ⚠ Not accounting for springback in bend design — work with your die maker to build compensation into the tooling.
- ⚠ Specifying zero burr — all stamped parts have burr. Specify an acceptable height and direction instead.
💡 Pro Tips
- ▸ For parts requiring both tight tolerances and bends, put critical features in early stations (before forming) where the strip is still flat.
- ▸ Carbide punches last 5–10× longer than tool steel — worth the investment for holes with tight tolerances.
- ▸ Our stamping factories in Vietnam run 50–400 ton presses with ±0.03 mm capable progressive dies.
- ▸ Request PPAP (Production Part Approval Process) documentation for automotive-grade stamping projects.
- ▸ Secondary coining after blanking can improve flatness and dimensional accuracy on critical features.
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