Shaft key can be defined as the piece of metal which is used for connecting the rotating machine element with shaft. It is generally used for the prevention of relative rotation between two parts and they are able in transmission of torque to take place. The rotating element (such as pulley, gear) and the shaft should have a key seat and a keyway for the proper functioning of a shaft key. A pre-cut slot is present in shaft in which one part of shaft key can fit and the other part of shaft key fit into a keyway which is a slot provided in the hub. The overall system is known as keyed joint and is able to provide relative axial movement between two parts.