A tailstock, also known as a foot stock, is a device often used as part of an engineering lathe

Lathe

A lathe is a machine tool which rotates the workpiece on its axis 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.Lathes are used in woodturning,...

, wood-turning lathe, or used in conjunction with a rotary table

Rotary table

A rotary table is a precision work positioning device used in metalworking. It enables the operator to drill or cut work at exact intervals around a fixed axis...

 on a milling machine

Milling machine

A milling machine is a machine tool used to machine solid materials. Milling machines are often classed in two basic forms, horizontal and vertical, which refers to the orientation of the main spindle. Both types range in size from small, bench-mounted devices to room-sized machines...

.

It is usually used to apply support to the longitudinal rotary axis of a workpiece being machined. A lathe center

Lathe center

A lathe center, often shortened to center, is a tool that has been ground to a point as to accurately position a workpiece about an axis...

 is mounted in the tailstock, and inserted against the sides of a hole in the center of the workpiece. A tailstock is particularly useful when the workpiece is relatively long and slender. Failing to use a tailstock can cause "chatter," where the workpiece bends excessively while being cut.

It is also used on a lathe to hold drilling or reaming tools for machining a hole in the work piece. Unlike drilling with a drill press or a milling machine

Milling machine

A milling machine is a machine tool used to machine solid materials. Milling machines are often classed in two basic forms, horizontal and vertical, which refers to the orientation of the main spindle. Both types range in size from small, bench-mounted devices to room-sized machines...

, the tool is stationary while the workpiece rotates. Holes can only be cut along the axis that the workpiece is set to spin.

Usually, the entire tailstock is moved to the approximate position that it will be needed by manually sliding it along its ways. There, it is locked in place and the tool mounted to it is moved with a leadscrew

Leadscrew

A leadscrew , also known as a power screw or translation screw, is a screw designed to translate turning motion into linear motion...

 to the exact position where it is needed. When a cutting tool such as a drill bit or reamer is used, the feed is done with this leadscrew. The tailstock quill or extendible portion usually has a Morse taper mount in the end of it to secure the drill or reamer. If the work is heavy the drill may be further secured from turning with a lathe dog as shown in the photo.