A lathe is a powered machine tool used to carve symmetrical shapes into metal, wood, or plastic by rotating the workpiece around a central point and using cutting tools (knives, chisels, drill bits, and gouges) to remove material until the desired shape is left. The most versatile type of lathe, and that described in this article, is the engine lathe.
Parts of the engine lathe
Engine lathes consist of a bed, to which the headstock, tailstock, and carriage are attached.
The lathe bed can be as simple as tubes on which the adjustable carriage and tailstock manually slide and lock over a feedscrew, or as complex as the machined steel tracks in which computer operated motors accurately place the carriage and tailstock for the reproducible manufacture of pieces to machined to highly precise specifications.
The lathe carriage consists of a tool rest atop the top slide and cross slide mechanisms. The operator rests handheld cutting tools against a tool rest in order to apply them to the rotating workpiece. The cross slide, upon which the top slide is mounted, permits perpendicular (front to back) adjustment so the operator can control depth of cut and cut tapers or curves into the workpiece by placing the tool rest wherever he needs it. The top slide, upon which the tool rest is mounted, permits longitudinal (right to left) adjustment so the operator can control left to right placement of the tool rest and make tapered or curved cuts.
Lathe carriages also typically have a toolpost for rigidly fixing cutting tools, instead of the operator holding the tools in his hand against the tool rest, which are then applied to the workpiece using the carriage's top slide and cross slide mechanisms.
The top slide and cross slide, as well as the placement of the carriage itself, are independently controlled by handwheels or electronics that move them relative each other and the workpiece.
The headstock unit is permanently fixed to the left of the operator. The headstock consists of a faceplate or chuck, to which the workpiece is fixed, attached dead-center to the rotating axis called the spindle. The spindle can either be mounted directly to a variable speed motor, indirectly mounted to a variable speed motor and/or spindle transmission by a belt, or indirectly mounted to a high-torque constant-speed motor via a gearbox transmission. Engine lathes used for light and heavy manufacturing applications are typically indirectly driven by a heavy duty motor attached to the spindle by a clutch and gearbox transmission.
The tailstock can either be used as a tool holder in the case of drill bits and cutting tools that need to be applied to the center or near the center of a workpiece, or it can be used to secure the workpiece itself with what are called centers. Centers are used to safely secure long or fragile workpieces that will then be cut from their sides using tools mounted to the toolpost or held against the tool rest in the operator's hands. Centers come in a variety of shapes to safely secure the workpiece based on the material it is made off and the operator's needs.
The tailstock is longitudinally adjustable along a feedscrew with either a handwheel or electronic controls.