NNP

Multiple Blanking.  The process of producing several blanks with a single stroke of the blanking press. A multiblanking head is required with a matching plate containing the same number and pattern of openings as the number and pattern of blanking punches. Such multiple blanking is highly suitable for coin blanks of thin gauge metal and small size blanks, as under one inch diameter.

The first multiple blanking had two blanking heads, and was called dual blanking. History has not recorded who developed this concept, but we do know that multiple blanking was done at the Royal Mint London by 1888. It was blanking silver shillings two at a time, and copper blanks – farthings and halfpence – five at a time.

As blanking presses developed, and became more powerful, additional blanking heads were added (with corresponding apertures in the blanking plate). The most modern multiple blanking presses can blank as many as thirty blanks with each cycle of the press. Wider strip is required and an elaborate blanking pattern is used. The advantage of multiple blanking is two fold: it lowers the cost of the blanks and slightly more blanks can be cut out of the strip (leaving as little as 30% to 35% unblanked, as skeleton  scrap).

Multiple blanking can create a number of errors from imperfect advancement of the rolled strip. Also portions of the skeleton scrap have been inadvertently struck, these mint errors are unusual shape. The most dramatic of such is the BOW TIE, struck on a piece of scissel from the metal formed between two dual blanking dies.  

`Leonardo da Vinci’s drawing (circa 1500) for a proposed press had, in effect, a blanking and a striking press back-to-back. Perhaps it could also do double blanking on the same strip (since these were completely separate of one another da Vinci could be credited with the concept, despite the fact there is no record this press was ever built).  See blanking.

    

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