The steel machine screw has a zinc plated finish and a pan head with a Phillips drive, and meets American Society of Mechanical Engineers ASME B18.13 specifications. Steel is often used in applications where strength 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 pan head has a flat top and short vertical sides with a rounded top edge.
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.