Forging is the plastic deformation of metals into desired shapes by
compression with or without a die. The basic principle of forging is that material flows
in the direction of least resistance.
The simplest forging operation is upsetting, compressing the metal between two flat parallel platens. More complicated geometries are achieved using dies.
Two basic categories of forging are open-die and closed-die. Drop hammers supply the energy through the impact of a falling weight to which the upper die is attached.
Another type of forging uses the mechanical press. (crank, knuckle, percussion and toggle.) Very large forgings use a hydraulic press operating at one-hundredth the speed of hammers. Other types are counterblow hammers (vertical) and impacters (horizontal).
