Lathe
Machine tools are machines for cutting metal. The most important machine tools used in industry are lathes, drilling machines, and milling machines. Other kinds of metalworking machines are not so widely used in machining metals as these three.
A lathe is a machine tool for cutting metal from the surface of a round work fastened between the two lathe centers and turning around its axis. In turning the work a cutter moves in the direction parallel to the axis of rotation of the work or at an angle to this axis, cutting off the metal from the surface of the work. This movement of the cutter is called the feed. The cutter is clamped in the tool post which is mounted on the carriage. The carriage is the mechanism feeding the cutter in the needed direction. The lathe hand may feed the cutter by hand or may make it be fed automatically by means of special gears.
The largest part of the lathe is called the bed, on which the headstock and the tailstock are fastened at opposite ends. On the upper part of the bed there are special ways upon which the carriage and the tailstock slide.
The two lathe centers are mounted in two spindles: one (the live center) is held in the headstock spindles while the other (the dead center) in the tailstock spindle.
The lathe chuck is used for chucking the work, which is for clamping it so that it will rotate without wobbling while turning. The chucks, usually mounted on the headstock spindle, may have different sizes and constructions.
If the work is perfectly round, it may be chucked in the so-called three-jaw universal chuck, all the jaws of which are moved to the center by turning the screw. But if the work is not perfectly round, the four-jaw independent chuck should be used.
In turning different materials and works of different diameters, lathes must be run at different speeds. The gearbox contained in the headstock makes it possible to run the lathe at various speeds.
Before turning a work in the lathe, the lathe centers are to be aligned; that means that the axes of both centers must be on one line.
The alignment of the lathe centers may be tested by taking a cut and then measuring both ends of the cut with a micrometer.
Not all works should be fastened between the two centers of the lathe. A short work may be turned without using the dead center, by simply chucking it properly at the spindle of the headstock.