A socket head shoulder screw has a shank diameter and length, and a reduced shank portion that is threaded. How is the screw measured?
For a socket head shoulder screw, the diameter listed is the diameter of the unthreaded shank, not the threaded portion. The length is that of the unthreaded shank only. The threaded portion is standard for screws of like diameters and will not vary regardless of the length of the unthreaded shank.