Thread cutting screw with type F point has machine screw threads that taper down to a blunt edge and is suitable for heavy gauge sheet metal, aluminum, cast iron, brass, and plastic Steel is often used in applications where strength is the primary consideration Zinc plating resists corrosion and has a reflective appearance Flat undercut head has a flat top with an 82-degree cone-shaped bearing surface and is undercut for use in shallow countersunk holes Phillips drive has an x-shaped slot that accepts a Phillips driver and is designed to prevent over-tightening