Here we see the Master Hub for the 1999-S proof Kennedy half dollars that is being carved in the same Janvier Reduction Lathe as seen in the previous photo. The device at the bottom of the Master Hub is doing the engraving. When the Janvier Reduction Lathe was introduced in 1907, the first two digits of the date began to appear on the galvano and thus on the master hubs. This was done so that the master hub could be used to make master dies over a period of several years. Starting with the Lincoln cents in 1909, the last two digits of the date were engraved into the master die for each year. By the middle of the 1980’s the Mint started placing the last two digits of the date on the master design (galvano). New master hubs were prepared each year for each denomination. At this time the Mint also started placing the mint mark on the master design for all Commemorative and proof coins. According to the 1986 Report of the Director of the Mint, the Mint was in the process of developing single-squeeze hubbing presses for the production of working hubs and working dies. According to that document, “During FY86 (Fiscal Year 1986 which actually began in 1985), the Mint further developed a new process for a key aspect of die manufacturing, the hubbing of dies in a single squeeze. When implemented, this will eliminate intermediate annealing and cleaning and the second hubbing operation. It will also avoid the possibility of hub-doubling (doubled die) errors caused by misalignment of the second squeeze. The new process has been used for master dies and work hubs and is in pilot testing for production dies.” In 1990 and 1991 the Mint began applying the mint mark to the master die for circulation strike coins. After 1994 the mint mark was placed on the master design. A major turning point for hub and die production in the U.S. Mints came in the summer of 1996 when the Denver Mint opened its own die making shop. Prior to this, all aspects of the die making process were done exclusively at the Philadelphia Mint. The new Denver die shop was equipped with the single-squeeze hubbing presses that the Mint started developing in the mid-1980’s.
Posted on: Sat, 20 Dec 2014 08:09:53 +0000
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