A lathe headstock is a geared transmission that provides power and rotation to various parts of the lathe. Internally, the headstock usually contains the follow major items: a motor, spindle, gearing or belt-driven transmission and various-sized bearings. The exterior of the lathe headstock can usually be identified by the a control hand levers, knobs or buttons. A collet or chuck, used to grip stock material, will extend out from the head lathe's headstock and completes the spindle assembly.
An electric motor will generally be found in the base of the headstock. This usually provides rotational power through a belt to the transmission. As the transmission turns, various gears and/or pulleys are adjusted either automatically or manually until the desired spindle speed and rotational direction is achieved.
Older lathes might not have an easily adjustable transmission. With these, access panels on the lathe headstock will need to be removed so the operator can reach the gears. After the gears are accessible, these can be reconfigured to the spindle's desired speed and direction. Some computer numerical control (CNC) lathe headstocks might contain a variable transmission, and this allows the computer control to change the speed and direction up or down as needed. Wood-cutting lathes are similar to their metal lathe siblings, but the wood lathe headstock will generally be of lighter construction.
Another style of headstock is found on a Swiss-style lathe. This Swiss style will have a sliding headstock designed to feed the stock material from the head toward the tooling through a guide bushing. The collet on a Swiss lathe is located behind a guide bushing.
Sometimes a chuck might be mounted at the tooling end of the spindle; this enables larger parts to be turned. If the material has a small diameter and is lengthy, it might be recessed into the hollow spindle and clamped with a collet. When the majority of stock material is contained within the spindle, the surrounding headstock offers additional protection for the operator. Some spindles might be tapered so that a center and lathe drive dog can be used to turn material.
Traditional engine lathes might also have an additional gearing system and lead screw built into and extending out through the headstock. This lead screw provides power to the lathe's carriage and adds versatility. All lathe headstocks, regardless of design or style, should be equipped with an emergency stop.