US Mint Videos: Upsetting Mill & Coining Press

US Mint - The upsetting mill raises rims around the edge on both sides of the blank and reduces it to a size that fits into the coining press collar. In addition, the raised rim helps protect the coin's design. The highest point of any coin design is always lower than the coin's rim. Raising the rim hardens the edge and helps keep the coin from eroding. This also helps the coins to stack.

The next stage of production is coining. This is the process of adding the design to the planchet. To strike the metal, one die (known as the anvil) is held motionless and the other die (known as the hammer) strikes the planchet's surface. The anvil is usually a reverse (or tails) die, and the hammer is the obverse (or heads).