The steel thread rolling screw for use in plastic has a zinc plating and a hex washer head. Steel is often used in applications where strength is the primary consideration. The zinc plating offers corrosion resistance and has a reflective appearance. The hex washer head has six flat sides that a wrench can grip to turn from the side, enabling use when there is no space above the head for a screwdriver. The flange acts like a washer to increase the fasteners bearing surface and distribute the clamping force over a larger area, providing grip and reducing damage to mating surfaces.
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.