A lathe is a machine tool which spins the workpiece to perform various operations such as cutting, sanding, knurling, drilling, or deformation with tools that are applied to the workpiece to create an object which has symmetry about an axis of rotation (Wikipedia ). Lathes perform the machining operation known as "turning." While turning, material is removed from a workpiece by rotating it against a tool. Turning is a central production operation in the manufacture of many metal, plastic and wood parts. Lathes can be either manually operated or computer controlled (CNC). Lathes can have many differences, unique features and accessories to facilitate a wide range of jobs.
The simplest lathe type is the wood lathe. As the name suggests, it is designed for turning wood. Wood lathes are small machines consisting of a bed, headstock, tailstock and tool rest. Unlike with what is found on a metal-working machine, there are no precision ways since the cutting tools are moved by hand and not by machine power. A steady hand and good skill is needed to control the cutting tool to accurately turn smooth curves and complex contours on the work piece. The spindle is driven by a belt connected to a motor, and speed differentiations are made by manually moving the belt to one of many pulleys mounted to the back of the spindle. Lathe tools are held by hand against the work, with the support of the tool rest. The tool rest is adjustable and is clamped to the bed at a position that best suites the operation at hand.
Engine lathes are the classic metal turning workhorses of the production machine shop. They come in many sizes and are flexible to working virtually any material. These machines have a longitudinal bed to which is mounted a headstock and tailstock. As in the wood lathe, the headstock contains the spindle. The spindle drive is more complex, including variable speed capacity or selectable gearing to provide a broader range of speeds. A carriage moves back forth on bed ways for longitudinal turning. A cross-slide and compound rest are mounted to the top of the carriage to provide cross and angled cutting capability. The lathe cutting tools are moved against the work manually using hand wheels or mechanically under the power of a lead screw that is driven by gears in the headstock.
The tool room lathe is a small- to medium-sized engine lathe specially designed for high-precision work. These machines find use in tool and die shops, where custom parts and precision fixtures are produced, frequently supporting production machining operations. Tool room lathes are manufactured with special attention to spindle accuracy, smooth operation and exact alignment of the carriage and cross slide. A tool room lathe is capable of better accuracy and precision than a standard engine lathe.
Turret lathes are used in production machine shops where several sequential operations are needed on single workpiece. It is expensive and time consuming to remove a workpiece from one machine and hold it in another. Removing and reholding a workpiece also cause errors in work alignment and machining accuracy. The turret lathe has a rotating turret mounted to the carriage so that as soon as an operation with one tool is completed, the turret is indexed to bring another tool into working position. The part is then machined again without having to remove it from the chuck or collet. Eight (or more) different operations can be performed on a workpiece using this type of machine.
Computer numerically controlled lathes have largely replaced engine lathes in production machining environments. CNC lathes offer the benefits of greater powered axis drives, feedback control to watch and maintain tool positioning and fast repetition of complex machine motions. Once a program is established, an operation can be quickly set up again without the necessity for tedious manual adjustments. CNC lathes do extremely well at cutting curved contours without the need for specially formed tools. This is done by programmed modification of the speed of two motion axes and the spindle simultaneously---an operation that is very unlikely with an engine lathe.