Definition

• Drop Forge.  Shaping hot metal by hammering with sudden heavy blows. Drop forge presses utilized the impact from a ram, operated by steam or electricity, as in a broad drop it rises to the height required for the amount of the force. The ram is released at the high point of its cycle and the ram falls by gravity. Power hammers, propelled by steam, increase the vertical thrust by double that of a gravity hammer (the ram is affixed to a piston rod to increase the force). The ram impacts a heated blank, called a billet or bloom. The plasticity of the molten billet permits the ram to force metal into all the die cavities. Temperature of the billet must be closely controlled; if heated too long or too high, for example, excess scale will be formed on the forged piece. Composition of forged pieces are almost always iron, though other metals may be used.
  Dies for drop forging must be designed to allow excess metal – flash – to exit somewhere, usually between the ram punch and the die block. After the piece cools the flash is ground off on a conventional grinding wheel. The ram punch and die block must be made of alloyed steel to withstand high pressure and severe stress of the forging.
  The process of drop forging is in contrast with cold coining (among other methods of metal forming). Cold coining may require repeated blows (with intermediate annealing), drop forging completes the design in one blow. As can be expected, the relief in a drop forged pieces is not as detailed as in cold coining, though the relief can be quite high. All cavities will be filled, but it will not have sharp crisp edges of lettering and detail. And the characteristic always exists of the ground off edge smoothing.

  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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