METAL WORKING MACHINERY, a term including practically all machines by which metals are converted into shapes required by modern structural work and the Industrial trades. They may be conveniently arranged under the following named classes: Lathes; borers or drills; punches; shears; milling machines; grinders; riveters; drop hammers; bending rolls; rolling machines; presses; planers; saws and special machines.
Lathes are turning machines used to ob tain cylindrical surfaces by rotating a bar of metal against a fixed cutting tool. They are also used for spinning sheet metal into form. The principal parts are the head stock holding the driving cone and revolving spindle; the tail stock supporting the back centre, and capable of being clamped at any point on the centre line of the bed or frame, and the rest or carriage bearing the tool head. The bar of metal to be worked is fastened to the head and tail stocks and rotated or turned by belts from shafting or by electric motors, while the rest carrying the cutting tool is moved parallel with the axis of the bar from the surface of which a spiral shaving is removed. By suitable attachments the lathe may be used for tooling flat surfaces, sawing or grooving and' cutting gear These machines are made in a great number of sizes, of which the principal forms may be designated as follows: (1) The hand lathe; driven by hand power, usually by a drill-bow, but sometimes by an assistant at the crank It is without self-acting feeding devices for regu lating the cutting tool. (2) The foot lathe; small and light, worked by the operator's foot and adaptable to work as delicate as that of the watchmaker and jeweler. (3) The self acting lathe; in which the cutting tool is held in a carriage which is moved by mechanical means, causing it to traverse automatically the object being turned — these lathes are adapted for screw cutting and are often so designated. (4) The chucking or face lathe; for turning cylinders several feet in diameter and many feet in length, such as engine cylinders and the tubing and jackets of large ordnance. The turret lathe belongs to chucking class, but the face of the chuck is horizontal, the revolving spindle being vertical. (5) The boring lathe,
used for working on internal cylindrical sur faces. A bench lathe is a small model of any of the several types so arranged that it may he bolted to a work bench. An automatic lathe is one of the larger types fitted with mechan ism by which it stops itself when the work it is set to do has been completed. Any lathe may belong to the single geared or back geared type. In the latter a set of gear wheels operates a back shaft, by which the speed of the work may be greatly reduced. Overhead shafting on the lathe standards or on the ceiling provides means for giving a revolving motion to the tools at work, thus a combined mo tion of great variety and intricacy for involved Borers or Boring machines, if op erated by hand power, are called ahand-drills,* otherwise, "power drills.) They are of two types, the horizontal and the vertical. The cutting tool is formed upon an axially rotating spindle designed to bore or drill cylindrical holes. They vary greatly in size and pattern; in the number of spindles employed and the man ner of their arrangement. Large holes, either horizontal, vertical or inclined, such as engine cylinders, tubing for ordnance and hollow shafting, are worked on a boring lathe, carrying usually two or more separate spindles clamped in a cylindrical tool head. Drills are especially useful as reamers to finish holes made by punches, and also to give exact cylindrical forms to the internal surfaces of hollow cast ings of any kind.
Punching machines are of the single or multiple type, capable of punching one or several holes at a time. They are used for punching rivet holes in boiler and armor plates, plates for girders and other structural metal work. The perforation is accomplished by the thrust of a cylindrical punch under great pressure. Though usually made to punch round holes they are also worked with "drifters* which square up the round holes. The power employed is steam or hydraulic, generated by individual engines for large and belt-driven ma chinery for small work.