Coin Manufacturing Process

Pre-processing

Individual governments have different ways of manufacturing their coins. The U.S. government uses metals like zinc and copper in the penny, while the quarter, nickel and other "silver" coins use different metals in their manufacture. Regardless of the metals used, though, there are a few steps that every coin manufacturing process has in common. It's these traits that allow the suppliers of metals for coins to keep their batches consistent, since it's necessary that they produce the same quality of product in exactly the same formula each time they deliver to the U.S. Mint.

The Milling Process

When the metal is delivered to the Mint for production, it comes in rolls that are in excess of 1,500 feet in length and more than a foot wide. These rolls weigh several tons and are delivered en masse. The Mint uses hundreds of these rolls annually to turn out the number of coins required to keep money flowing.

The coiled metal is unrolled into a long sheet and fed through a press, which cuts out coin-shaped discs that are smooth on both sides. These blanks, each of which is called a planchet, are then moved via a conveyor belt into a furnace. The furnace heats the metal discs to make them far more malleable, and then they're moved into a washing tank. This tank thoroughly washes the blanks to ensure even stamping and then they're moved into a drying area. The heat in the drying area removes the excess moisture from the coin-shaped blanks and they're vibrated through a screen which sorts them according to size. Only a single batch can be run through a machine at any given time, since coins of different size would fail the screening process.

The blanks are then moved into a rotary mill which puts a ridge around the edge of certain coins. After the blanks are given ridges, they're rolled into a press that stamps the official design onto the blank. It's this stamping process that turns them into genuine U.S. tender. Of course, sometimes the coins are incorrectly stamped. These coins occasionally get past the quality control department and into general circulation. It's these coins that are most often regarded by coin collectors to be valuable.

Quality Control

Since the U.S. Mint turns out millions of coins each year, the quality control process is an arduous one. Both the stamp operator and the quality control division check the coins, and each division is responsible for maintaining the high quality to which the Mint aspires. The coins are checked optically via camera and the naked eye, but other quality control measures are a closely kept secret by the Mint.

References

• Homepage for the U.S. Mint