How the U.S. Mint Manufactures Circulating Coins.

Introduction

Each day millions of Americans pass around small change without pausing to consider where those shiny metal discs originate or how they are manufactured. Under the well-known images of former presidents and various symbolic designs lies a complicated manufacturing process carried out by the United States Mint. The Mint has main facilities in Philadelphia, Denver, San Francisco, and West Point and uses heavy industrial machinery together with great care and skill to produce billions of coins every year. By understanding the method of production one can see how raw metal is systematically turned into a dependable and durable currency which supports daily commerce.

The First Steps of Coin Manufacturing.

The process of manufacturing starts with the first stage, known as blanking, and then involves annealing in high-heat furnaces. In order to produce standard circulating coins such as quarters, dimes, and nickels, huge coils of metal—which can be as long as 1,500 feet—are fed into a blanking press. This high-speed machine is able to punch out circular metal discs, or blanks, at a rate of up to 14,000 per minute, the excess metal webbing being shredded and recycled. Since the punching operation hardens the metal, the raw blanks have to be annealed, which is a thermal treatment carried out in an oxygen-free furnace heated to as high as 1,600 degrees Fahrenheit; the heating process softens the metal structure so that it can take the intricate die impressions without cracking in later stages.

Forming the Planchet

When they have been softened, the blanks are washed, dried, and then go through a process called upsetting to give them an edge shape. Immediately after coming out of the furnace, the hot blanks are dropped into a quench tank containing a cooling mixture of water, citric acid and lubricants. They are then thoroughly washed using anti-tarnish agents in order to regain their shiny metallic appearance and are dried with heated steam. The next step is to feed the smooth blanks into an upsetting mill, where each disc is pushed through a groove that is only slightly narrower than its own diameter. This pressure causes the metal to rise up along the edges and form a raised rim. Only when a blank has acquired this protective outer rim—a feature that prevents the coin's future design from being worn down and enables the coins to be stacked—is it officially known as a planchet.

The Striking Stage: Transforming Planchets into Legal Tender.

The process by which a simple planchet becomes legal tender takes place at the striking stage. The planchets are sent to high-speed coin presses, where upper and lower steel dies—each having the coin's obverse (front) and reverse (back) designs engraved on them—imprint both sides at the same time. The operation involves enormous forces, varying from 35 to more than 100 metric tons of pressure, causing the soft metal to flow directly into the raised areas of the dies. Exactly at the instant of impact, a surrounding collar holds the planchet in place, stopping it from spreading out while at the same time giving its edge a smooth, reeded, or lettered finish. A single circulating press is capable of striking up to 750 coins per minute, which allows facilities such as those in Philadelphia and Denver to produce tens of millions of coins each day.

Quality Control and Distribution: The Final Stage of the Coin's Journey.

In the last stage, the new coins are subject to a rigorous quality check before being put into packaging for distribution. To do this, inspectors take samples to look for mistakes and coins that do not meet the required standards; those coins which fail the inspection are passed through a machine known as a waffler, which bends them into wavy pieces so that they can be melted down and recycled. The coins that pass the quality test are then sent through fast counters, weighed to ensure accuracy, and placed into large bulk storage bags. The U.S. Mint then sends these coins to the Federal Reserve Banks all over the country, where they enter the banking system and end up in cash registers, vending machines, and people's pockets, thus completing an amazing cycle of engineering and production.