Coining is a cold working process that uses high pressure to plastically deform a workpiece between a punch and die to conform to their shapes. The metal flows under compressive forces to take on the impressions of the completely closed dies. Coining provides a finer, more detailed surface finish than other metal forming processes and work hardens the surface. It is commonly used for minting coins and medallions, making jewelry, badges, buttons, springs, and complex electronic and precision parts that require close tolerances and smooth polished surfaces.

2. Concept
 Introduction
 Technique of coining
 Advantage of Coining
 Industrial Application

3. Introduction
Coining is a cold working process that uses a great deal of force to
plastically deform a work piece, so it conforms to a die. The coining
process consists of die and punch. By using the punch and die, the
impression and image are created on metal. The pressure involved in
coining process is about 1600Mpa.
The metal flows plastically and squeezed to the shape between the
punch and die . The metal is caused to flow in the direction of
perpendicular force . The type of impression is formed by compressive
forces. The type of impression obtained on both side will be different.
Coining can be done using a gear driven press, a mechanical press, or
more commonly a hydraulically actuated press. Coining typically
requires higher tonnage presses than stamping, because work piece is
plastically deformed and nor actually cut. The coining process is
preferred when there is a high tonnage.

4. Techniques of coining
Completely closed dies are used for this process.
High pressure is applied on the closed die containing
the metal work piece.
As the result of the high deformative stress, the metal
conforms to the shape of the die.
Lubricants are not used in coining as they are
incompressible .

5. Advantages of coining
Provide finer and detailed surface finish.
Provide accurate bends in a consistent manner.
Does not require expensive machinery.
The work hardened surface can resist impact abrasion.
Eliminate the need for complex finishing process.
Plastic flow reduces the surface grain size and work
hardens the surface.

6. Industrial Applications
Minting of coins and medallions
 Making of jewelry
Making badges, buttons, precision-energy springs
Making complex electronic parts
Making precision parts that require finer polished
surface finishes.
Note:- In coining pressure is applied on the surface of
forging in order to obtain closer tolerances, smoother
surfaces and eliminate draft.

7. END