it consists of a dead center surrounded by hardened teeth, which bite into a softer workpiece allowing the workpiece to be driven directly by the center. this allows the full diameter of the workpiece to be machined in a single operation, in contrast with the usual requirement where a carrier is attached to the workpiece at the driven end. the use of modified shell end mills in a drive center, instead of hardened pins, enables better gripping and prevents breakdown time due to pin stop.