Definition Of a Planchet
A planchet is a prepared disc-shaped metal blank onto which the devices of a coin image are struck or pressed. The metal disc is called a blank until the time it passes through the upsetting machine which causes the rim to be raised. Once it has a rim, the disc is called a planchet.
When referring to ancient coins, and coins which were made from cast metal discs rather than machined metal discs, the generally preferred term is flan.
There are really no hard and fast rules about the usage of these terms in ancient coin collecting, and you will sometimes hear ancient coin blanks referred to as "planchets." In modern machine-made coinage, the distinction is very clear: the disk is a "blank" before getting the rim, and a "planchet" afterward.
Why Do We Need a Raised Rim?
Before the blank is sent to the coining press it needs to go through a process that slightly squeezes the blank in order to put a raised rim around the periphery of the coin. This serves several purposes:
- It helps provides a uniform diameter to the coin so that when it is injected into the coining press it will fall squarely into the coining collar. The collar holds the planchet and place so the coin dies can make a clean strike in order to produce a finished coin.
- The raised rim also helps to ensure that under the intense pressure of the coining press the metal will flow uniformly into the deepest recesses of the coining die. This is important in order to obtain a high-quality coin. This also helps to ensure that a uniform impression is achieved on each and every coin.
- Usually, the raised rim is one of the highest elements of the coin. Since this extends around the entire periphery of the coin it helps protect the design from being worn off the coin while it is circulating in commerce.
During the production process of coins, the first step is to punch a blank out of a metal sheet of uniform thickness. During the production process of this metal sheet, there are several errors that can happen. Here is a partial, but by no means all-inclusive, list of planchet errors:
- Missing Metal or Holes: Initially, the metal starts off as a hot liquid and is formed into an ingot. The ingot is then rolled until it is a uniform thickness that is required for the coin being minted. During this process, gas bubbles and cracks can form resulting in holes or missing metal in the planchet.
- Thick or Thin Planchets: Human error can result in the rolled metal being too thick or too thin. If this is not detected by quality control, the sheets of metal can go on to produce planchets that are not within the production tolerance for the coin being minted.
- Laminations: Most coins are made from an alloy where two or more different metals are mixed together. If the mixing process is not uniform ribbons of improperly alloyed metal can appear in the planchet.
If you have a blank planchet and are looking for more information about it, see my page on blank planchet errors.
When modern coins are being struck, the planchet is fed into a coin press, which stamps the images onto the coin.
Edited by: James Bucki