Clutches, brakes, and drive components transfer torque and prevent mechanical overload. These drive components include clutches and brakes, splined hubs and shafts, and torque limiters. Clutches and brakes transmit power to control starts and stops in mechanical power transmission systems. Splined hubs and shafts are also used to transfer torque. They consist of an involute splined shaft with grooves and teeth that match a hub or coupling. As the shaft rotates, the locking grooves move the hub or coupling and transmit power. Torque limiters are used to automatically prevent mechanical overload. Also known as overload clutches, these units come in two main forms. Friction-style slip clutches allow the load to slip, while shear pins disconnect the load through shearing and must be replaced after each overload.