The class 4.8 steel machine screw has a zinc plated finish and a flat head with a Phillips drive, and meets Deutsches Institut für Normung DIN 965 specifications. Class 4.8 steel, composed of either low or medium carbon steel, is often used in applications where toughness is the primary consideration. The zinc plating offers corrosion resistance and a reflective appearance. 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. The flat head is cone shaped for use in countersunk holes and has a flat top that fits flush with the mated surface.
Machine screws are threaded fasteners that are typically used with nuts or drilled and tapped (threaded) holes. Machine screws are available with a variety of head shapes, which determine how the screw interacts with the mating surface, and drive styles, which determine the type of driver required to install and remove the screw.