Mint details Apollo 11 coin production challenges
- Published: Dec 21, 2018, 5 AM
Executing dies for the production of the Proof 2019-P Apollo 11 50th Anniversary 5-ounce silver dollar proved to be a considerable challenge for the United States Mint.
The four coins in the commemorative coin program — silver dollars measuring 1.5 inches and 3 inches in diameter, a gold $5 coin and copper-nickel-clad half dollar — all feature common obverse and reverse designs, with the obverses being concave and the reverse convex.
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Ronald Harrigal, manager of the Mint’s design and engraving division, explained to Coin World Dec. 13 that the working dies manufactured for coin production are actually master dies.
Harrigal provided an explanation of the design process after the ceremonial first strikes of the 1.5-inch silver dollar and 3-inch silver dollar were produced at the Philadelphia Mint.
Like the 3-inch coin, the 1.5-inch dollar is composed of .999 fine silver, the first commemorative silver dollar struck in .999 fine silver instead of the usual 90 percent silver, 10 percent copper.
The blanks for the 1.5-inch silver coins are supplied by Sunshine Mint from Coeur d’Alene, Idaho, and Leach Garner from Attleboro, Massachusetts. Sunshine Mint also supplies the 3-inch silver blanks.
Harrigal said all future legislation seeking standard 1.5-inch silver dollars will have a provision stating the composition will contain not less than 90 percent silver, giving the Mint latitude in selection of coin blank fineness depending on availability from vendors.
In developing the degree of curvature for the Apollo 11 commemorative coins, calculations were first determined for the 3-inch silver coin, and then adapted to the remaining three coins.
Changes in process
The Mint’s current process differs markedly from only a little over a decade ago. Circa 2006–2007, the Mint phased out its use of the Janvier reduction lathe in the die production process. The Mint’s Janvier lathe had been used in die production for a century, having first been introduced in die production for Saint-Gaudens’s gold $20 double eagles in 1907.
That process had required execution of plaster models or copper galvanos, which would be mounted in the Janvier machine, where a stylus would trace the coin model as a cutting tool simultaneously cut the reduced design into die steel, thus fabricating a master die.
That master die would be hubbed — impressed under high pressure into annealed or heat-softened die steel — to execute a master hub from which working hubs and then working dies would be made for actual mass coin production.
The plaster model step and several others have been eliminated with the retirement of the Janvier lathe, which is on display at the Philadelphia Mint as part of a public walking tour.
Today, members of the U.S. Mint’s engraving staff can either execute two-dimensional designs and have them scanned into a computer for final artistic manipulation, or model their designs in 3-D clay models, from which another physical model can be executed on Ren board, another modeling material.
Mint production technicians take the final renditions of the digitized designs and impose the final specifications for relief and depth of basin and design elements.
Once a final rendition with technical specifications is approved, the results are delivered electronically to a computer-controlled (CNC) cutting machine that cuts the master die.
For the Apollo 11 3-inch coin dies, the raw dies cut on the CNC lathe are manually finished and cleaned up to remove burrs and other errant metal before undergoing laser-frosting and Proof polishing of specific design elements.
Finding the curve
Harrigal said design and engraving personnel were challenged to get the curvature correct on the 3-inch coin so that the dies would fit properly on the 1,000-ton-capacity press. The curvature is referred to as a “compound curve” as it required multiple variables to define.
Initially, there were problems with proper metal flow filling the relief, Harrigal said. There were specific fill problems at the astronaut’s hands, the American flag and lunar lander, he said.
Die cracks appeared along the legs of the lunar lander Harrigal said. Relief specifications were adjusted to eliminate the die fill problems and cracking.
Some of the problems were more pronounced when using the traditional 90 percent silver blanks, but were easily corrected with the softer .999 fine silver blanks, which allowed for smoother metal flow.
The Apollo 11 designs were much more intricate than the curved 2014 National Baseball Hall of Fame commemorative coins, and Mint technicians had to work with adjusting some of the details, for example the height and angle of lettering, some of which extended to the edge and was the first part of the die to contact the blank during striking.
Harrigal said that, when it was determined that the production dies would be each individually machined, the process was reduced from 14 hours per die to 11.5 hours. With a sellout being projected, it’s likely 1,000 pairs of dies will have to be prepared.
The finish treatments are executed by machinery outfitted with templates that delineate the portions of the designs that will receive the various respective treatments.
A color-coded schematic illustrated nearby defines what devices were subjected to standard frosting, heavy frosting and Proof polishing.
The faces of the dies then receive a PVD (physical-vapor deposition) treatment that applies a protective coating to extend die life.
The obverse, designed by Maine artist Gary Cooper as winner of an open design competition, was sculptured by U.S. Mint Sculptor-Engraver Joseph F. Menna. The reverse design, mandated under Public Law 114-282, was sculptured by U.S. Mint Sculptor-Engraver Phebe Hemphill.
The obverse features as its central device a footprint on the lunar surface.
The reverse features a representation of a close-up version of the famous Buzz Aldrin on the moon photograph taken July 20, 1969, that shows just the visor and part of the helmet of astronaut Aldrin. The reflection in Aldrin’s helmet includes Neil Armstrong, the United States flag and the lunar module.
The 3-inch silver dollars are being struck on a German-made Graebener GMP 1000 press. The press was assembled circa 2009–2010 in the basement of the Philadelphia Mint.
The press, the only one of this type owned by the Mint, was acquired for dedicated production of 3-inch silver quarter dollars for the America the Beautiful Quarters Program in bullion and Uncirculated versions.
The Apollo 11 3-inch coin is a Proof-only issue, with 100,000 coins maximum authorized.
The 3-inch blanks are struck three times under approximately 460 metric tons of pressure per strike. The blanks are hand-fed into the coinage chamber by press operators wearing cotton gloves.
After striking the finished coins are removed with rubber-tipped tongs or by gloved hands.
The 3-inch coins are being struck at the rate of 13 coins per minute, based on three strikes per coin at a striking speed of 39 coins per minute.
The actual number of coins struck per minute is much lower since each blank is hand-fed between the coinage dies in the coinage press and removed by hand after being struck into a coin.
All 100,000 coins maximum will be struck on blanks hand-fed into the press by press operators wearing cotton gloves.
And there is only one press capable of producing the 3-inch silver Proofs, the same press used to strike the 5-ounce silver American the Beautiful quarter dollars in bullion and Uncirculated versions.
Harrigal said each coin is inspected after striking for defects and the dies are cleaned frequently to remove grease and prevent debris build-up.
The dies are oriented in the press horizontally, with the obverse die being the moving upper hammer die, and the reverse being the lower, stationary anvil die.
The 1.5-inch silver dollars, the gold coins and the copper-nickel clad half dollars are being struck on Graebener GMP 360 coinage presses with the same die alignment as the 3-inch silver versions.
The Proof and Uncirculated 1.5-inch silver dollars and Proof 3-inch silver dollar will be produced at the Philadelphia Mint with the P Mint mark.
The 1.5-inch silver dollars have a maximum combined authorized mintage of 400,000 coins.
Presses will be able to produce 500 to 600 coins per hour, with the Proof coins receiving three strikes each at 185 metric tons per strike.
U.S. Mint officials have not disclosed the number of strikes nor tonnage per strike for the Uncirculated versions of the $5 gold, 1.5 inch silver dollar and copper-nickel clad half dollar coins. The Proof and Uncirculated gold $5 coins will bear the W Mint mark of the West Point Mint where the gold coins will be struck.
The Proof gold coins will receive three strikes at 70 metric tons of pressure per strike.
For the copper-nickel clad half dollars, with a maximum potential mintage of 750,000 coins, the Proof version will be struck at the San Francisco Mint and bear the S Mint mark, and the Uncirculated versions, struck at the Denver Mint, will carry the D Mint mark.
Three strikes will be required for the Proof version, at 130 metric tons per strike.
Coin World observed the striking process for the 5-ounce silver dollar.
A protective gate retracts and a 3-inch coin blank is hand fed into the coinage chamber by a press operator wearing cotton gloves. The blank is placed resting on the reverse die.
The press operator then simultaneously presses two buttons, dropping the protective gate back into place and engaging the press to begin striking at a speed of 39 strikes per minute.
After three strikes, the dies retract, releasing the finished coin for retrieval by the press operator, when the protective gate mechanically lifts for the process to be repeated.
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