A shoulder screw has a smooth shank top, or shoulder, with a narrower, threaded tip at the bottom. These screws are often used in engines and mechanical applications to allow for rotation of pulleys, linkages and other moving parts. Typically, separate dimensions are specified for the shoulder and the threaded part of the shaft. A shoulder screw is often called a shoulder bolt or, when used to attach a stripper plate, a stripper bolt. Whether you are doing repairs, maintenance or assembly, Grainger has the shoulder screw for the job, from standard socket head screws to metric self-locking screws.