By Stephanie Meredith
August 26, 2020
Blank. Planchet. Upsetting. Burnishing. You may have heard these words before, but what do they mean? Learn about these terms to better understand how the U.S. Mint makes coins.
To review the parts of a coin and the different coin finishes, such as proof and uncirculated, read Anatomy of a Coin.
After a coin is selected and a digital sculpt finalized as described in part one of this series, die making begins the production process. In the die making process, the Mint makes several generations of hubs and dies. Hubs show a positive image the way the artist created it. Dies are like a photo negative, displaying the design in reverse. Dies act like a stamp to transfer the designs onto the coins.
The Mint buys large metal coils 1,500 feet long to cut out blanks. Blanks are flat metal discs that will eventually become coins or medals. A blanking press punches out blanks from the coil like a cookie cutter.
Blanks are annealed in a furnace to prepare them for striking. Annealing changes the physical properties of the metal to make it softer and allow it to be shaped without breaking. The annealed blanks will hold the design better during striking.
To transfer the annealed blanks to the washer, the Philadelphia Mint uses a cylindrical rotating machine called a whirlaway. The Denver Mint uses a large scoop called a skip basket.
After washing, the blanks travel to the upsetting mill. Upsetting means to “upset” the edge of a coin to create a raised rim. Some people also call this step rimming. The rim protects the final coin from wear and makes it stackable.
A blank with a rim is called a planchet, although it’s acceptable to continue to use ‘blank’ as a general term for a coin before it’s struck.
Special proof and uncirculated planchets go through a cleaning process called burnishing to smooth and polish the surface using metal pellets.
Finally, the planchets travel to the coin presses for striking. Striking happens when the press forces the obverse and reverse dies together to transfer the design onto the coin.
The coins are inspected for defects and then sent for packaging. If circulating coins don’t meet certain standards, the batch goes to a machine called a waffler. The waffler bends the coins to form wavy lines before they’re sent for recycling.
- How Coins Are Made: The Design and Selection Process goes through how coins are designed and a final design chosen.
- How Coins Are Made: Bringing Coins Into Circulation includes the process the Mint and the Federal Reserve use to get coins into circulation.
- Anatomy of a Coin describes the parts of a coin as well as circulating, uncirculated, and proof finishes.
- Coin Production describes how coins were made from the 18th century to today.
See more Inside the Mint articles.