Without upsetting machines we could not have high-speed coining. Yet few people know about them, particularly the coin collecting community. The later do recognize that something happens to coin blanks before being struck into coins, because they refer to coin blanks as “type one” and “type two.”
Early coins were struck on screw presses – one at a time – and the need for a perfectly round, perfectly shaped blank was not that great. Coin blanks at the time were hand fed into the screw press with a blank nearly the size of the coin being struck.
Amazingly, while two men swung the arms of the screw press driving its shaft up and down, the coin setter flicked off the struck coin and placed the blank or planchet into position for the next striking. Once they established their rhythm, they could strike 20 or more coins per minute.
The actions of one man, Mathew Boulton (1728-1809), of Birmingham England, changed all that. He joined with a partner, James Watt (1736-1829) who had invented the first successful steam engine, to seek new ways of putting the power of steam engines to good use. Boulton had inherited a metalworking factory, so this was an ideal association.
Boulton was a manufacturing genius. He had the ability to put together all the right factors – men, money, and machines. He was so resourceful in this that he is credited with being a notable pioneer in the Industrial Revolution. His search for products to make eventually led him to produce coins. He established the Soho Mint in 1790. He hired away from the Paris Mint one of the most talented coiners of all time, a Swiss die-engraver and engineer, Jean Pierre Droz (1746-1823).
Under the direction of Droz, they altered the screw press to be powered by the stream engine, but the increased power and increased speed brought forth many new problems. Nevertheless, Droz was capable of solving all of these. His talents extended from making the dies, using stronger iron (supplied by Benjamin Huntsman, who in 1756 had invented a method of making crucible steel), cutting dies on a French reducing machine developed by Jean Baptiste Dupeyra, to improving the screw press and adding an automatic feeder.
Droz had brought the technique of that feeder from Paris. While at the Paris Mint in 1783, he and Philippe Gengembre had jointly devised a way to feed the blanks and remove the struck pieces while the screw press was still manually operated.
With Boulton’s backing and Droz’s talents each of these problems were addressed, often creating new equipment and new methods of coining. Of course, Droz also solved a problem with blanking: as coin blanks are sheared from the rolled, milled strip of metal, they are often left with sharp burrs on the trailing edge.
If the blanks were not perfectly round, or those burred edges were prominent, it caused jams in feeding the press. If greater minting speed was to be achieved, Droz knew he needed blanks in large quantities that were uniformly edged and perfectly round for the automatic feed.
At first they hired young Birmingham boys – some as young as 8 to 10 years old – to put a handful of blanks in a leather bag and shake the bag. The blanks knocked against each other and “deburred” the edges.
Remember, this is the beginning of the Industrial Revolution, so they had to find a better, faster way. Next, they tried putting the blanks in a barrel and rotated the barrel, a process similar to what is called “barrel tumbling” today. This tumbling process is accelerated by adding steel balls smaller than the blanks to knock against each other. The steel balls can be sieved out later.
Droz’s solution was a method of pre-forming the blanks. He recalled a technique of edge thickening developed in 1649 by Frenchman Pierre Blondeau (ca1620-1664), which was later improved upon by another French engineer, Jean Castaing, who in 1685 developed a device of adding edge lettering or edge ornamentation.
Both these methods were similar in that they forced the blank between two grooved bars, one fixed and one that moved back and forth. Boulton, who had been working on the problem of edge thickening at his metalworking factory since 1788, had to wait until it was solved by Droz in 1797.
Droz devised a way to force round blanks between a rotating grooved disk with a fixed bar in the shape of an arc with a similar groove. He mechanized this rimming action with the rotating disk, powered by the factory steam engine.
At the Soho Mint they called this method “rimming” and the machine a “rimmer.” These terms are still used in England today.
In America we call this action “upsetting” and the equipment an “upsetting machine.” At the U.S. Mint they call it an “upsetting mill.” Elsewhere it has been called “edge marking” as well. So much for the terminology.
A later contemporary of Boulton, Ralph Heaton (1794-1862), founder of the Heaton Mint, obtained one of Boulton’s rimmers and modified it slightly. He manufactured these rimming machines and sold them to mints around the world along with presses he manufactured after having acquired the rights to build Uhlhorn-style coining presses.
His firm, Ralph Heaton & Sons, patented a device in 1859 that fed blanks into the rimmer to further speed up the total process. In the United States, the Heaton rimmer was modified slightly. Instead of a vertical rotating disk, a different method was developed at the Philadelphia Mint with a horizontal wheel forcing the blanks between this rotating, grooved disk and a fixed, grooved arc-shaped bar.
A further development occurred at the British Royal Mint. In 1860, a mechanic working there, Meredith Jones, developed a method of rimming with the groove on the face of the rotating disk. He called his machine the “Jones Marking Machine.” It had the advantage that it could be easily altered for different diameter blanks.
Upsetting Among Mint Secrets
Knowledge of this machine, like that of many mint techniques, was among the most closely guarded secrets at many national mints. A topmost secret was the aperture collar and how to upset blanks. All during the nineteenth century, mint personnel were pledged not to reveal any facts about these techniques, presumably to prevent counterfeiting. The penalty was to have a hand chopped off!
Modern upsetting machines still perform the functions of their predecessors. Using collectors’ terms, type one blanks are those before upsetting, type two after. A type one blank fed into an upsetting machine travels in a channel on a spiral track through ever smaller and smaller walls which forces the blank’s diameter to become less and less. The metal at the edge builds up on both surfaces, thus making the blank thicker around the circumference, ideally suited for striking raised-rim coins.
By pressure and rolling, the pre-forming of edges by the machines accomplishes the following:
- Remove the burrs and smooth the edge
- Round the edge
- Make the blank perfectly round
- Thicken the edge for a raised border – edge thickening – a typical metalworking process
- Make every blank a uniform diameter, always several thousandths of an inch less than the aperture in the collar used in the coining press.
- Reduce wear on both dies and collar.
For proof blanks, upsetting provides a prepared edge ready to create a sharper and more angular point at the rim-edge juncture on proof surface coins. Ideally this should be close to a 90-degree angle without any excess metal forming a wire edge.
A Collector Asks…
In 2004, one of my readers on E-Sylum, Chris Faulkner, asked two questions about upsetting machines: how do they work and who uses them?
Obviously they are used by coinage mints, but who else?
I live near the Naugutuck Valley of Connecticut where machine shops and metalworking plants are on every block in every industrial area (after all, this was the home of Scovill Manufacturing and the Brass Industry for 150 years). Some of that industry still exists in the area today.
The obvious answer is many of these plants that strike anything “coined” – that is, struck between dies at room temperature – use the upsetting technique. This includes buttons, small parts, washers, rings, the list is lengthy. Some odd-shaped parts are coined from round blanks because of the ease and speed of striking these. They are then trimmed to shape afterwards.
I learned of the upsetting machine close up when Medallic Art Company bought its first coining press in 1967. We bought the press in Germany, but upsetting machines are made in England (and still called “rimmers”). The firm could not obtain one right away.
My boss, Bill Louth, happened to mention this to Eva Adams, then Director of the U.S. Mint. “We have some we’re not using,” she said. “I’ll lend you one.”
Sure enough, until a new one came from England, Medallic Art Company used a U.S. Mint upsetting machine for upsetting blanks to strike medals! The first of these were the Illinois Sesquicentennial Medal of 1968 in silver dollar size. The company soon had its own delivered from England and returned the borrowed one.
Today, Medallic Art Company and Northwest Territorial Mint use upsetting machines to prepare blanks for a wide variety of medallic and bullion products.