Définition

• Spark Erosion.  Cutting an exact one-to-one replica in metal by electrical discharge machine (edm). The process vaporizes metal in micro amounts creating very tiny micro cavities. If a die is cut by edm these micro cavities can be buffed and polished on flat surfaces, particularly in the fields on numismatic items or dies, but not in recessed areas; thus a piece struck from a die made by edm will exhibit a surface of multiple micro bosses from the micro cavities.  See also electrochemical metal removal.

  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

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