Coining

Coining plastically displaces metal in a closed die to create crisp details, precise thickness, and excellent surface finish in high-volume stamped parts.

Overview

Coining, or coin stamping, is a high-pressure metal stamping process that forces material to flow within a tightly closed die. It forms very fine surface details, sharp edges, and highly controlled thickness in localized areas. The process runs cold, so parts come off the press with excellent surface finish and minimal springback.

Use coining when you need logos, text, serrations, calibration steps, or sealing surfaces formed directly into a stamped part. It shines on small to medium parts with tight dimensional and cosmetic requirements at medium to high production volumes. Tradeoffs include high press force requirements, more expensive tooling, and limits on feature depth relative to sheet thickness. Over-coining can cause cracking or excessive work hardening, so designs need to respect material and thickness constraints. Coining is often used as one station in a larger stamping process to refine critical areas rather than form the entire part.

Common Materials

  • Low carbon steel
  • Stainless steel 304
  • Aluminum 1100
  • Aluminum 5052
  • Copper C110
  • Brass C260

Tolerances

±0.0005" to ±0.002" in coined regions

Applications

  • Currency and medals
  • Logos, text, and branding on hardware
  • Fine serrations and knurls on levers or knobs
  • Sealing lands and gasket surfaces
  • Indexing features and detents
  • Thickness calibration pads and shims

When to Choose Coining

Choose coining when a stamped part needs very crisp details, controlled local thickness, or high cosmetic quality in specific areas. It fits best for ductile metals, shallow features, and medium to high volumes where tooling cost can be amortized. Specify it for local refinement operations, not for forming large 3D shapes.

vs Progressive Die Stamping

Choose coining when the critical requirement is ultra-precise local detail, sharp edges, or surface finish that standard progressive forming cannot hold consistently. Coining can be integrated as one station in a progressive die, reserved only for the most critical surfaces to control cost and press tonnage.

vs Transfer Die Stamping

Use coining instead of relying only on transfer forming when you need localized calibration of thickness, flatness, or cosmetic detail after the main form is created. Coining can follow transfer operations to lock in sealing surfaces, datum faces, or identification marks with much tighter tolerances.

vs Deep Drawing

Pick coining when you need shallow embosses, logos, or sealing lands on relatively flat or mildly formed parts, not deep cups or shells. Deep drawing builds overall 3D shape; coining refines surface detail and dimensions in limited regions with higher precision.

vs Blanking & Piercing

Choose coining when the part needs more than just cut geometry—such as embossed text, calibrated steps, or work-hardened edges for wear resistance. Blanking and piercing define the outline and holes; coining is used to upgrade key areas for function or appearance without secondary machining.

Design Considerations

  • Limit coined feature depth and height to a reasonable fraction of sheet thickness to avoid cracking and excessive thinning or bulging
  • Keep coined features a safe distance from part edges, bends, and holes to prevent distortion and edge cracking
  • Clearly identify which surfaces are truly critical for coining so the toolmaker can focus tonnage and die detail where it matters
  • Use generous radii and smooth transitions around coined areas to reduce stress concentration and extend die life
  • Specify realistic surface finish and tolerance bands for coined regions based on the material and press capability, not generic machined-callout defaults
  • Align part orientation and feed direction so coined features can be supported by robust die steel and adequate backing, especially on very small details