The steel thread rolling screw for use in metal has a black oxide finish and an 82-degree flat undercut head with a Phillips drive. Steel is often used in applications where strength is the primary consideration. The black oxide finish offers mild corrosion resistance and lubricity. The flat undercut head has a flat top with an 82-degree cone-shaped bearing surface and is undercut to a lower head height for use in shallow countersunk holes. The Phillips drive has an x-shaped slot that accepts a Phillips driver and is designed to allow the driver to slip out of the head to help prevent over-tightening and damage to the thread or fastener.Thread cutting and thread rolling screws, two types of self-tapping screws, are threaded fasteners that create a mating thread in the wall of a hole. The two screws differ from each other in the way that they create the threads. Thread cutting screws cut the wall of the hole to create the thread, creating material chips that need to be cleared away from the hole to prevent clogging. Thread rolling screws, also called thread forming screws, do not remove material but instead press against the wall of the hole to displace the material and form the threads.