A machine screw is a fastening screw with a machine cut thread throughout the length of its shank. Machine screws are used with nuts or screwed directly into a threaded receptacle to fasten various components together in machines, tools and more. Fasten with a screwdriver to reduce risk of over-tightening and protect the screw and fastened material. If nuts are needed, use with nuts of the same finish and threading for proper fit. The length of a machine screw is measured from under the head to the point of the screw.