It is usually used to apply support to the longitudinal rotary axis of a workpiece being machined. A lathe center is mounted in the tailstock, and inserted against the sides of a hole in the center of the workpiece. A tailstock has a Dead Center, while Head stock has a Live Center. 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, the tool is stationary while the workpiece rotates. Holes can only be cut along the axis that the workpiece is set to spin.