The theory “If man can make it, man can made it better” doesn’t always hold true. Two cases in the history of manufacture of coins and medals – coins particularly – proves that point.
Ever since 1506 when Italian Donato Bramante modified a fruit press to blank sheets of lead, to make seals for Pope Julius II, we have had a mechanical way of striking coins, ultimately using this technique on a screw press.
The mechanical genius Leonardo da Vinci about the same time sketched such a screw press in his notebooks – whether it was ever build in his day is doubtful. Da Vinci theorized a single blow of a screw press could cut out a blank at the same time impressing an image on the front and back of a previously made blank.
It proved successful to do these in separate operations.
Thus coins struck in a press start from rolled out strips, which are then blanked to produce the circles of metal, then struck in a press. The process is called milled coinage from the milling of the metal to a required thickness before blanking in a rolling mill.
The process is also called cold coining — the blanks are not heated, both blanking and striking is done at room temperature.
Rejected technique number one. Coins have been made since 640 BC. A lump of metal was placed on a lower die fixed to an anvil. The upper die was placed on top of this lump and it was hit with a heavy blow a number of times until it was flattened and took the image of both dies.
Called hammered coinage, the process continued for a long time. Since it was simple, elaborate factories were not needed to make the coins. It was more of a cottage industry where issuing authorities allowed individuals, called moneyers, to strike the coins. They could keep one coin for every 16 they made. The authorities controlled this by supplying the dies, but, obviously, false reporting ran rampant.
It was probably one of those moneyers in Rome who thought he could make his job easier, or perhaps make more coins in quicker time. Could he make a coin quicker by heating the blank?
The answer was NO. The heated blank did not expand uniformly when impressed by the dies. Metal flows outward from the center of the blank’s surface to the edge. The heated blank flowed unevenly, some areas reaching the edge ahead of adjacent areas. The coins had ragged, saw tooth edges. This result is known as hot tears, unsatisfactory for a disk of metal made into a coin.
The first use of moneyers was in 104 BC. But even after the screw press and other devices for coining became available, the moneyers did not stop. They fought hard to keep their franchise.
By 1553 a gifted mechanic from Augsburg, Eugene Bergeron, brought his coining technology to the Paris Mint and attempted to establish a more modern method of coining, in effect creating the birth of milled coining. Yet he was driven out of Paris in 1560 by the moneyers who learned his technology would replace their lucrative activity.
This occurred in England as well in 1561. Not until 1662 – a century later – did the moneyers become entirely replaced by a milled coinage with the use of the screw press. In 1641 the screw press was reintroduced, permanently, at the Paris Mint, and in 1662 at the London Mint.
Rejected technique number two. Two years before Bereron’s trip to Paris, another Augusburg mechanic, Kaspar Goebels, came up with the idea of roller die coinage. Instead of blanking strips of metal first, then striking the coins, Goebels idea was to impress the images on a strip of metal with a roller die first, then cut out the coins.
The German word for this process was taschenweke. The name of the roller mill specially engraved with the coin images on a roller was called a walzenwerke. Goebels attempts to use his process in Denmark, and later Spain. It had problems of registration, the obverse image had to match the reverse image, also the trimming or cutting out of the image exactly from the strip was also critical. The technique was a failure at both mints.
In 1637 no less than the chief engraver at the Paris Mint, Nicholas Briot, attempts roller die coinage again. It fails again at the Paris Mint. He is dismissed, travels to England and gets the job as chief engraver at the Tower Mint. There he tries a roller die coinage again without success.
Finally at the Edinburgh Mint in Scotland he is named mintmaster. He finally achieves somewhat of a satisfactory roller die coinage, but it only works for a large diameter coin. The process falls into obscurity, never to be attempted again.
Never? Would you believe it was tried again in the 20th century by no less an institution than General Motors!
In 1964 U.S. Treasury officials met with several top GM officials and discussed the cent shortage. Even with three-shift production of cent coins, the Mint could not meet the demand to end a cent shortage.
GM vice president Louis C. Goad – he was head of manufacturing – told Mint officials he could build a press which could produce 10,000 coins per minute. The Mint took him up on the challenge.
He assembled a group of engineers and mechanics at GM’s training center in Michigan. They build a press and between 1964 and 1968 tried three times, three different ways.
Among several minor problems, the major problem was that the action generated a tremendous heat. In effect, it melted the dies. The process failed again and in 1969 they closed down the experiment.
Thus within the 2,652 years of coin-making technology we have 460 years of successful coin making by cold coining, milled technology. A heritage of blanking a strip of metal to create proper thickness blanks which are then struck in a press one at a time!
The technology works for creating coins. Forget roller die coining. Or heating the blanks.
Resource: Read more on that General Motors experiment: http://usrarecoininvestments.com/coin_articles/gm_roller_press_cent.htm