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A tailstock is a drill bit that, in rotary motion machine tools such as a conventional or numerically controlled lathe, serves to support the workpiece on the opposite side of the spindle during machining using chip removal tools. It is usually rotating as the workpiece rotates with the main spindle. It is inserted into a body where it mounts axially loaded precision roller bearings, and is prepared with different shanks or attachments depending on the lathe head in which it is mounted. The drill normally has an axial preload created with cup springs that generate axial compensation so that it exerts a constant load on the workpiece during machining.

A rotating tailstock to be mounted on a lathe is commonly chosen to support and make a workpiece rigid during a radial or longitudinal turning operation. It is normally used in the following cases:
- When workpieces with a projection from the main spindle of around 2-3 times the gripping diameter are produced
- When the mass of the rotating workpiece is particularly heavy
- When longitudinal turning must be particularly cylindrical and precise.

The tailstock can also be used fixed and can also be applied on a milling machine or machining centre if it is necessary to support shafts during milling and/or grooving operations in order to avoid any geometric misalignment with respect to the axis of the workpiece, vibrations caused by bending of the workpiece during the milling operation.

In order to optimise the choice of a tailstock, it must be borne in mind that its function is mainly to keep the workpiece on axis during machining by preventing it from rotating off-axis, preventing vibrations, turning with a roundness error, a surface with excessive roughness, poor tool life.

But the reason that makes it most important in its use is to prevent the workpiece from swinging off its centre until it comes out of the jaws of the chuck, so without control it can cause damage to the machine tool, but even worse the out-of-control workpiece can hit and seriously injure the operator on the machine.

The tailstock must be chosen according to the following parameters:
- Type of shank or shank attachment
- Mass of the workpiece
- Rotation of the workpiece during machining
- Precision cylindricity of the workpiece
- Precision roundness of the workpiece
- Quantity of workpieces to be produced
- In the case of difficult workpieces and long shafts
- Choose whether it should also be used as a drag chuck,
- Selection of the correct cusp according to the tool dimensions.

Preparing the workpiece for insertion of the tailstock:
- Drill a hole with a centre drill with a countersink angle equal to the angle used for the drill head
- In the case of insertion in a hole, choose the drill head according to the chamfer created at the start of the hole.

Scheduled tailstock maintenance: Tailstocks must still be checked between uses by checking the radial or axial play of the precision bearings. When replacing bearings, also replace any axial compensation springs.