Modern Coin Production
A mint is simply a factory at which coined money is made. The processes through which a coin is made are in many ways very similar to how many other products are produced. Here's how it works.
From Design to Hub
The designs for coins are first sketched by an artist, then made into a modeling wax or plasticene bas-relief model, typically by a mint employee called an engraver. This model will be about three to twelve times larger than the diameter of the proposed coin. A plaster negative is cast from this model, and then the design on the model is retouched to refine the details as necessary, with appropriate legends (inscriptions) added. A plaster positive model is then made from the plaster negative.
What is a coin galvano?A galvano is the model for a coin design that serves as a lathe before the design is transferred to a coin-size hub.
Once this hard plaster model is approved by the appropriate authorities, a hard epoxy composition model is made from this same plaster model. The epoxy model is mounted on a Janvier transfer engraving machine, a machine that reduces the design to the appropriate size for the coin as it transfers the image onto a master model for the proposed coin called a hub.
From Hub to Coinage Dies
The hub is heated to harden it, then it is placed in a hydraulic press. The hub is hydraulically pressed into a blank piece of soft die steel until a negative duplicate image appears on the soft die steel. This is called a master die. Working hubs are made from the master die by again using a hydraulic press to transfer the coinage image. Working coinage dies are produced from the working hub. These dies will be used to strike coins until they wear out, at which time new working coinage dies will replace them. In theory the finished coins should be identical regardless of which coinage die is used, since all coinage dies originate from the same working hub. (In fact, on occasion a collectible coin variety may inadvertently be made when something alters the features on an individual working coinage die or on the working hub from which the working coinage dies are made.)
Coinage Blank Production
The appropriate metal for the individual coinage denomination is assayed for purity, melted, and formed into ingots. The ingots are rolled into long strips of the appropriate coinage thickness. The strip is coiled for storage until needed. The strip is fed into a blanking press to punch out coinage blanks of the appropriate weight and diameter. The blanks are sifted through a bedplate with holes of the correct diameter for quality assurance. Burrs are removed from the edges of each coinage blank in an additional quality assurance operation.
The approved coinage blanks are heated, or annealed, to about 1,400 degrees Fahrenheit, then given a water bath to keep their crystal structure consistent to this softened state caused by the annealing process. The coinage blanks are given a chemical bath to remove any discoloration caused by the annealing process. Then the coinage blanks are blow dried. The coinage blanks are given a slightly raised edge rim by passing through an upsetting mill. Obverse and reverse coinage dies, and an appropriate diameter collar to hold the blanks are set up in a coinage striking machine. Coinage blanks are fed individually by gravity from an overhead hopper into the coinage striking machine. The coins go through a final quality control inspection, and then they are bagged for shipping to Federal Reserve banking centers.
Other Mint Functions
The primary mission of any mint is to produce coins. Typically minting business strike coins is this primary mission, however collector coins may also be made, or in a few rare instances collector coins may be the only product made by a privately owned mint. Other mint products may include bullion (precious metal) composition trade coins, refined metal, and bank notes and security paper products such as stocks and bonds.