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 form around the circumference of the coin blank. Once it has a rim, the metal disc is called a planchet. When referring to ancient coins, and coins made from cast metal discs rather than machined metal discs, the generally preferred term is flan.
There are 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 obvious: the disk is a "blank" before getting its rim and is a "planchet" afterward.
Before the Planchet
Before the mint makes planchets, rolls of metal approximately thirteen inches wide and rolled to the precise thickness for the coins being made arrives at the mint. Each roll weighs several thousand pounds and has a natural curve due to being rolled up for ease of shipping. Mint workers first place the roll into a machine that flattens the metal to remove the natural curvature.
It is then transferred directly into a blanking machine which punches 10 to 20 blanks out of the roll simultaneously. The sheet of metal is now full of many holes. This leftover material from the blinking process is called webbing. The webbing is then chopped into smaller pieces called chattel. The chattel is then recycled and used to make more coins.
You can see from the photo above that the manufacturing process leaves many imperfections on the surface of the blank. Before the coin is fed into the coining press, it goes through a process called annealing, which softens the metal. Softening the metal makes it easier for the coining press to in part a full and complete image onto the planchet. Each coin is struck with several tons of pressure that removes any nicks and gouges on the surface of the planchet.
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 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 fed into the coining press, it will fall squarely into the coining collar. The collar holds the planchet in place, so the coin dies can make a clean strike 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 process is important to obtain a high-quality coin. Additionally, the collar also helps to ensure that a uniform impression is achieved on every coin.
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 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. If the mixing process is not uniform, ribbons of improperly alloyed metal can appear in the planchet.
Another area of coin collecting covers blank and planchet errors.
Edited by: James Bucki