The ductility of many metals, including many of the alloys, is sufficient to allow sheets of the metals to be pressed cold, without injury, into a great variety of forms. A considerable change of shape from the flat sheet may be accomplished by a succession of gradual changes, as was seen in forming large tubes in the operations of making hot-drawn tubes. The amount of distortion which can be accomplished at each step depends upon the power applied, and upon the ductility of the metal. The metal must be annealed after a certain degree of change of shape, else its ductility is lost and further pressure would disrupt the piece.

Common examples of the application of this process are cartridge cases, small round tin boxes, embossed metal ceilings, man-hole covers for boilers, metal ends of lead pencils, spoons, and many domestic utensils.

Many articles are pressed completely at one operation, and many others of more complicated shape are pressed in two or more successive operations under different dies, with or without annealing, according to the ductility of the metal used. This process is now applied to the shaping of articles from cold plates of mild steel as great as % of an inch thick, although the thickness of steel which can be shaped cold is limited only by the power of the shaping press and the ductility of the steel.

The machines which shape thin sheets do their work by power transmitted through geared wheels, levers, cams, etc., to properly placed punches, dies and plungers, and the proper lubrication of the work is essential. These machines are built to turn out work with a minimum of attendance, and many of them carry a piece of metal through the several steps and turn out the finished product automatically so long as sheet metal is fed to them.

The shaping of heavier sheets, particularly those of steel, usually requires hydraulic presses, although very powerful machines are built for heavy work similar in design to those for lighter work.

As with all metal-shaping processes, particularly do these processes require means of holding the metal to be shaped firmly in the position or positions required.