The stainless steel machine screw has a plain finish and a flat head with a star drive. Stainless steel resists corrosion and may be magnetic. The star drive, also called a Torx drive, has a six-pointed indentation that provides a large contact area for the driver, resisting slippage better than a Phillips or slotted drive. A star drive requires use of a Torx driver for installation and removal. 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.