Diameter: 1/4 Length: 3/8 Material: Steel Finish: Zinc Head Style: Pan (Phillips) Thread Size: 20 (Coarse) Thread Length: Full Type: Machine Screw Box of 100. A machine screw also called a stove bolt is generally a smaller fastener threaded the entire length of its shank. Machine screws are used in fastening nearly all types of hard materials. Especially useful in metal-to-metal or where heavy duty fastening is required. Commonly used with flat or lockwashers.