Essential Numismatics: The Minting Process By Ryan Greene My friend David once said, “Everyone makes mistakes”, but attaining a firm grasp on the minting process will make it very tough to make a mistake in determining an error’s origin and rarity! Mint errors make us think hard about the minting process and all its parts. Knowing the ins and outs of the minting process is essential in understanding how an error came to be and why it is so valuable. You will understand by the end of this article how metal goes from a large brick to a coin in your pocket! In this process we will use nickel because the fact of it only being one layer and no plating makes the description of the process easier to understand. When coins are ordered by the Federal Reserve for commerce it is the U.S. Mint’s job to create them. The first thing the mint would do is call the warehouse and order coin sheet coils. These coils can weigh between 6,000 and 8,000 pounds and be almost a mile long! Let’s say they were out of nickel coil, just for explanatory purposes. The coil manufacturer would bring in the brick of nickel to be processed and feed it into a rolling machine set on the highest level, because it takes literally tons of pressure to thin the block into a sheet of blank thickness. This process is repeated many times adjusting the rollers lower and lower until it reaches the right thickness. Next, once the coil is rolled tight and secured, it is shipped to the warehouse where it will await its call to use by the mint. When a coil is called in it is shipped to the mint on a flatbed and is unloaded on the dock near the blanking punch. A ceiling crane picks up the coil and the workers feed an end into the punch. A blank punch can blank, for example, 14,000 dimes a minute. A blank is a metal disc that is punched out of the coil strip and is the earliest stage of a finished coin. The amount of nickels blanked a minute would be less because they are thicker, larger and stronger than a clad dime sheet. The coins are placed on a conveyer to the next process. The next process is the annealing furnace. Gas heated and turning like the cylinder of a cement truck, this oven soars up to 1400 - 1700 degrees to burn off impurities and to soften coins for the upcoming striking press process. The blanks head on a short conveyer to the washer and dryer where they are heavily washed in a number of chemicals, one being cream of tartar. Next to the dryer where they are again heated and are rid of all moisture. The blanks then head to a machine called an upsetting mill. This is the part of the process where a blank is fed into a wheel that progressively tapers slightly pushing the outer rim of the blank a forming a raised metal ridge called an upset rim. This process has now produced what is known as a planchet. This planchet has its rim upset to assist the die in striking up the coins design well and causes it to fit better in the coin striking chamber. After the planchets are struck it makes it easier to stack them with a raised rim. Because the heads of the presidents aren’t square, these raised rims protect the design and makes the coins more durable. Before we get to the final process of coin creation, an important stage must be covered, called the die making process. Dies are what strike the coins and impress a design into the coin’s surface. This process starts out with an artist’s drawing which is then transferred by the artist into a large plastilene model (commercial modeling clay). The model is coated in graphite, which conducts electricity, and is lowered into a copper plating wash. This process attracts copper molecules to the designs surface. Eventually a thick copper layer forms and is a perfect representation of the design on the inside of the layer. This layer of copper is then filled with Plaster of Paris. When dry, the plaster is removed and is an exact replica of the plastilene model in the beginning. This 15 inch model is then placed on an antique pantograph machine, called The Janvier transfer-engraving machine to reduce the large engraving models to actual coin size onto the end of a bar of steel. This engraved steel bar will eventually become The Master Hub. Two of the machines still in use are over 90 years old. The Master Hub is used to strike multiple Master Dies which, in turn, strike multiple Working Hubs per Master Die. Each Working Hub strikes a multitude of Working Dies, which strike the coins. The Denver mint uses anywhere from 500-2000 dies a week. These dies and hubs are cut down from 10 ft. ball bearing rods into 3 inch mini rods, so to speak. Each die on average can withstand 500,000-1,000,000 strikes. Off we go again to the next process, the coining presses. The mint has completely switched over from Bliss presses to Schuler presses. Schuler presses are much more efficient and create much less errors. These new presses strike horizontally where the Bliss presses struck vertically. Coins are fed in by little chutes and the machine strikes about 750 coins per minute. The coins are caught in a holding chamber where they wait to be checked by an inspector with a loupe. If all is well, the press operator opens up the catch door and the coins pour into a rolling bin where they are pushed over a chute on the floor. The chute leads to counting machines below. The counting machines count and weigh every coin that goes into the ballistic bag underneath the counting device. This process takes about 20 – 25 minutes. The ballistic bags are made of nylon and Kevlar and weigh about a ton. From here the bags are lifted by a forklift and are stored at an undisclosed location where they are staged to be shipped as soon as the Federal Reserve requests. The minting process is very interesting. Without it there would be no coins. Technology is constantly changing the way we mint and also increases the likelihood of the mint catching errors before they escape, making it harder and harder to obtain errors for collectors. The error collecting is full of excitement and discovery, so enjoy every minute of it! Most of the numbers used in this post were from the mouths of mint representatives themselves. I have been to the Denver mint many times and always take notes. They always have way more to tell than I could ever get down while walking...lol
A Highly informative and well written subject piece. Cable Tv often re-runs their segment on the U.S. Mint Process, however this subject specifically is not covered. Insightful and a good read. Thank you.
Very interesting. I never knew the raised rims were there to protect the design and make them last longer also. Makes perfect sense and a good idea to help make them last longer and more durable.
