Hydraulic Press. A press whose action or force is derived by hydraulic pressure – liquid forced into a cylinder. Hydraulic action delivers great force in a slow and distinct squeeze; large medals can be struck on this type press, also the dies themselves can be hubbed on a hydraulic press. (See hubbing press.) Coinage presses are not hydraulic because of their slow squeeze; coinage presses require greater speed. Leonard da Vinci envisaged hydraulics and made such drawings in his notebooks.
excerpted with permission from
An Encyclopedia of Coin and Medal Technology
For Artists, Makers, Collectors and Curators
COMPILED AND WRITTEN BY D. WAYNE JOHNSON
Roger W. Burdette, Editor