Types Of Metalworking Lathes

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A lathe, in its simplest form, is a machine that holds a work piece and turns it so that operations, such as cutting or sanding can be performed on it. Metalworking lathes come in many types designed for specific purposes. Some of these types are engine, CNC, speed, hollow spindle, turret, swiss-type, metal spinning, polishing, etc. The operations that can be performed on a lathe are as varied as the types. Lathes can cut, thread, drill, bore, polish, sand, face, chamfer, etc. The most common lathe found in almost all metalworking shops is the engine lathe. All the operations listed above can be performed on an engine lathe - these are handy machines to have around.

The engine lathe consists of a headstock with a spindle in it, a tailstock, a bed with ways, a carriage and a tool post. The headstock sits on the left end of the bed and contains all the gears and mechanisms to turn the spindle. The end of the spindle is equipped with a method of attaching various work holding devices, such as chucks, faceplates, and collet chucks. The tailstock is located to the right of the headstock and can be moved along the bed to accommodate ...
... shorter or longer parts. In the tailstock is a taper in order to hold various devices, such as drill chucks, centers, drills, etc., exactly in line with the spindle. In between the headstock and tailstock is the carriage. On top of the carriage is the tool post. The carriage is designed to be able to move the tool post in two axes of motion, towards and away from the work piece (the Z axis) and across the face of the work piece (the X axis). With these basic components many operations can be performed and a wide variety of parts can be made.

A CNC lathe is a lathe where the carriage motions are controlled by a computer program. This computer program actuates servo drive motors that turn screws that move the carriage in the X and Z axis. Most CNC lathes are also able to change the speed of the spindle and change tools. To change tools the CNC lathe is most often equipped with a turret in place of a simple tool post. This turret can be indexed to bring various tools to bear on the work.

Lathes use ways to allow the moving parts - the carriage and tailstock - to move precisely and align them accurately. The spindle is held in the headstock with bearings designed to prevent deflection from cutting forces and keep the spindle firmly in line with the bed ways. Deflection is a potential source of accuracy problems in all lathes. Engine lathes have feed gearboxes and feed screws to provide power and motion to the carriageThese gearboxes are made in such a way as to provide feeds that allow certain desired threads to be cut in the work piece. This capability is duplicated in CNC lathes through the use of ballscrews and servo feed motors.

Most metal lathes incorporate some form of coolant system where a cooling stream of fluid can be directed on the work piece at the point of the cutting tool. This fluid can be water or oil based and lubricates the cut as well as cooling the tool and work piece. Coolant is typically caught in a coolant pan or tray and directed into a tank where a pump pushes it back up to the cutting area. The coolant also serves to wash the cutting debris (called swarf) away from the work area.

Metalworking lathes are absolutely essential to the manufacture of all modern machines - every machine, from a bull dozer to an aircraft is full of lathe turned metal parts. Modern life as we know it could not exist without metal lathes.