METAL-WORKING MACHINERY. The number and variety of metal-working machines are very large, the term comprehending prac tically all machines by which metals are wrought into useful shapes. For ordinary purposes metal working machines may be divided into the fol lowing classes: Planing machinery or planers; turning machinery or lathes; boring machinery or drills; punching machinery or punches; milling machines; machines or shears; riveting . machinery or riveters; presses; bending Drachm , cry; saws; and specie] machinery.
PLAxixo 'MACHINES. Planing machines or I planers are employed for working metal surfaces to accurate planes by cutting off the projections P by the planing or cutting action of a suitable past which the work reciprocates or revolves in a fixed plane. One of the most common forms of planing machines is shown by the illustration. ( Fig. 3, Plate of METAL-\ onKING MACHINERY.) The tool is carried by a tool head having a slid ing motion on a crossbar which can be moved up or down on two vertical guides. The table which carries the work clamped to it slides back and forth between the two vertical guides, and thus brings the work against the tool, which takes off a narrow, thin shaving of metal. By a suc
cession of such shavings following each other like the furrows of a plowed field, a plane surface is secured. Machines of this character are built in various sizes, some of them having tables 21 feet long and 7 feet wide. In rotary planers the work has a rotary motion with respect to the tool instead of a rectilinear motion. Planes for smoothing the edges of metal plates usually have the work clamped fast while the tool is carried along the edge taking off a thin shaving. Power is usually supplied to planing machines from shafting by means of belt transmission, and the rotary motion of the belt is transformed into the reciprocating motion of the table by means of gearing. When in operation the motion of the table and the motion of the tool head necessary to produce successive cuts are automatic.