Definizione

• Center Point.  The exact center of a model, dieshell, hubshell, hub, die, or thusly, the struck piece from any of these. For a hand engraved die, the center point may show up as a tiny boss on the struck piece from the indentation of a compass leg on the die. This is particularly true for softer metals, as some gold coins struck from hand engraved dies often exhibit a center point. For modeled coins and medals, this center point is critical for the positioning of the tracing point – and the cutting tool – on a die-engraving pantograph that starts in the center.
  The center point on a die is found by triangulation of three points outside the die
  line (see set lines); in a drawing, by a compass; in other items by measurements. On
  a die-engraving pantograph the center is found by placing the tracing point into position and a wad of clay on the approximate center of the dieshell or pattern; the tracing point is allowed to penetrate the clay and the pattern is rotated one full circle; the depression in the clay is examined under magnification. It should show an even circle around the tracing point with no gaps, proof that the tracing point is set dead center.

  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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