fly press
noun
a hand-operated press in which a horizontal beam with heavy steel balls attached to the ends gives additional momentum to the descending member used to punch or compress material
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
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Examples from the Web for fly press
Historical Examples of fly press
The stamp is urged by a fly-press, which cuts them out at one stroke.
Plated buttons are stamped by the fly-press, out of copper-plate, covered on one side with silver at the flatting-mill.