Coining (machining)

Coining is a form of precision stamping. It differs from simple stamping in that enough pressure is used to cause plastic flow of the surface of the material. A beneficial feature is that in some materials, such as phosphor bronze, the plastic flow breaks up the surface crystals, work hardening the surface, while the material deeper in the part retains its strength, toughness, ductility and flexibility.

Coining sometimes uses several dies to produce near-net shapes.

Coining is used to produce money (coins), precision-energy springs and precision parts with small or polished surface features.