Steps to Minting Coins

Designing the Coin

Coins begin as images and text that must be transferred to the two sides of a metal disk. Two detailed clay models record every aspect of each side of the future coin. These clay models can be up to four times the size of the finished coin. The large size is necessary to give the sculptor freedom of movement and expression. Positive and negative plaster casts are made of the finished clay model. These are used to produce another model that is coin-sized. Casts taken from these smaller models are used to make the high-carbon steel dies that will be used in the actual minting process. Good quality steel ensures that a die can be used again and again without losing its ability to record fine detail. Two dies are made: one for the obverse, or heads, side of the coin, and one for the reverse, or tails, side of the coin.

Making the Blanks

The appropriate metal is made into small disks called blanks. Most modern coins are made of base metals, like copper, nickel and zinc. Some special issues are produced in gold or silver, as were most larger denomination historic coins. The metal is rolled into thin sheets. Numerous contemporary coins are also clad coins, that is, they contain a core of one metal, and a coating of another metal or combination of metals. The cladding must be fused to the exterior of the metal sheet. The metal sheets roll through blanking presses that punch out the blanks. The rough-edged blanks have their edges smoothed, and all the blanks go through a process of annealing where they are heated to a temperature of 1400 degrees F. Annealing softens the metal, making it less brittle, and better able to withstand the force of continued striking. A rim is added to the blanks, and the blanks become planchets, ready for minting.

Producing the Finished Coin

For the actual minting, the two dies are fitted into a press. The lower die, or reverse, forms the anvil, or fixed portion of the press. The obverse die becomes the hammer, or movable part of the press that will actually strike the coin. Planchets fall into the press through a cylindrical tube. In some machines, a pair of feeding fingers grasps the lowest planchet and places it into the press. In others, the planchet drops into a dial feeder, a disk with holes that resembles the dial on an old rotary phone. The hammer slams against the anvil with the planchet in between. Depending on the design and the hardness of the metal, the planchet may need to be struck several times. Modern technology also permits the strikes to be of different intensities. Ridged edges and other features of the side of the coin are added by the collar that holds the coin in place during striking. The completed coin is dislodged from the anvil and hammer. Final processing includes cleaning and polishing, and in some cases, adding a mirrored or antiqued finish to the surface of the coin.

References

• Designing and Minting the Coin
• Producing the Blanks
• Striking the Coin