Set Screw

A set screw is a type of screw generally used to secure an object within or against another object, normally not using a nut. The most common examples are securing a pulley or gear to a shaft. Set screws are usually headless, meaning that the screw is fully threaded and has no head projecting past the major diameter of the screw thread. If a set screw has a head, the thread will extend all the way to the head.