Manufacturing Process for U.S. Coins

A major alteration was made in the content of the United States one-cent coin in 1982. It was changed from the standard alloy of 95 percent copper and 5 percent zinc to copper-plated zinc. The five-cent coin is composed of a homogeneous alloy containing 75 percent copper and 25 percent nickel. The ten-cent coin, quarter-dollar coin, half-dollar coin and one-dollar coin are all "clad" coins, produced from three coin strips that are bonded together and rolled to the required thickness. The face of these coins is 75 percent copper and 25 percent nickel and the core, which is visible along the edges of the coins, is composed of pure copper. In 2000, the United States Mint released the Golden Dollar coin, changing the alloy of the dollar coin to a clad composition manganese-brass, containing 88.5 percent copper, 6 percent zinc, 3.5 percent manganese, and 2 percent nickel. More information about the specifications of U.S. coins can be found on the United States Mint website.

All of the materials used for producing our coins are purchased from commercial manufacturers. The United States Mint obtains one-cent coin blanks already made, but produces the blanks for five-cent coins and the cupronickel clad coins from strip. Coin strip is fed into high-speed automatic presses which cut the coin blanks, known as planchets.

The cupronickel planchets are softened by annealing in a special furnace, then they are cleaned in large rotating barrels which contain a chemical solution that washes and polishes them, and then they are dried.

Next, the planchets are put through an edge-rolling operation in the upsetting machine. This gives them the familiar thickened edge found on the one-cent coins and five-cent coins. It also serves two other purposes. The edge hardens during the upsetting process, thereby preventing soft metal from squirting between the collar and the dies during stamping. It also removes any burrs and smoothes the edge, making it easier to automatically feed them into the high-speed coin presses.

Finally, the upset planchets go to the coinage presses, where with a single stroke, they are stamped with the designs and inscriptions that make them into coins. Most of the presses are equipped to strike four coins simultaneously, while others simultaneously strike two coins.

Generally, the manufacturing process is the same for all denominations, except that the edges of dimes, quarters, half-dollars and dollars are marked with tiny ridges. This process is known as "reeding". It is done by a collar which is a part of the stamping operation. More than just a decoration, reeding was originally intended as a preventative measure to discourage the illegal shaving or clipping of the precious metal in the gold and silver coins. It has been retained on today's cupronickel clad coins not only in deference to a long-standing practice dating back to colonial days, but also as a distinct aid to the visually handicapped.

After striking, each coin is inspected. The coins are then counted and bagged. Each bag is weighed before shipment to ensure that it contains the correct number of coins.

The final step in the manufacturing process is when the United States Mint ships the newly-made coins to the Federal Reserve Banks for distribution into the economy through the banking system.

Last Updated: 11/13/2010 8:18 PM