Definition

• Engine for stamping blanks to make coins. The lower die is fixed into an anvil, generally wedged or fastened with set screws, to discourage loosening and rotation or chatter. Blanks are positioned atop it by open collar (prior to 1829) or in the coining chamber by close collar (beginning in 1829). The upper die is mounted at the end of what is essentially a rotating pile driver: a column fitted with screw threads, caused to descend rapidly with great force by rotating two weighted arms attached to the upper end of the column. The arms are attached to ropes pulled by workmen or horses, depending on press size; only the smallest presses could be operated by two laborers plus the moneyer. Larger presses could serve not only for larger coins but for stamping hubs into working dies, or raising hubs from matrixes. The inventors were Renaissance medallists attempting to rediscover how the ancient Romans made coins in high relief. Some features of the screw press are credited to Leonardo da Vinci; others to Boulton & Watt, including the automatic feed and safety devices in use at the Philadelphia Mint since 1793.

Quelle

• Breen Encyclopedia

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