chief difference between hand forging and machine forging is that in the
latter technique various types of machine-powered hammers or presses are used
instead of hand sledges. These machines enable the operator to strike heavy
blows with great rapidity and thus to produce forgings of large size and high
quality as swiftly as required by modern production-line methods. Another
advantage of machine forging is that the heavier the blows struck during
forging, the greater the improvement in the quality of metallic structure.
Fine-grain size in the forging, which is particularly desirable for maximum
impact resistance, is obtained by working the entire piece. With large,
hand-forged metal, only the surface is deformed, whereas the machine hammer
or press will deform the metal throughout the entire piece.
A special type of machine forging is drop forging, also called impact-die forging. Drop forging consists of placing soft, hot metal between two shaping dies (see Die). The upper one of these dies is hammered, or dropped, on the lower die, forcing the heated metal into the shaped die cavities, as in coin-making operations.
reducing part of a piece of metal stock to a predetermined size, forging
rolls are sometimes employed. These consist of a pair of grooved, cam-shaped
rollers through which the metal is passed. The rollers touch each other and
work on the metal during only part of each rotation and therefore reduce only
part of the stock that is fed to them.
operations are frequently accomplished by use of a series of dies mounted on
the same press or hammer. The dies are arranged in sequence so as to form the
finished forging in a series of steps. After the piece has been partially
formed by one stroke, it is moved to the next die for further shaping on the
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