A shoulder screw differs from machine screws in that the shank is ground to a precise diameter, known as the shoulder, and the threaded portion is smaller in diameter than the shoulder.
Shoulder Screw, 18 (Coarse) Thr Sz, 7/16 in Thr Lg, Steel, 5 PK Shoulder bolt specifications call out the shoulder diameter, shoulder length, and threaded diameter; the threaded length is fixed, based on the threaded diameter, and usually quite short. It is usually used for revolving joints in mechanisms and linkages; when used as a guide for the stripper plate in a die set its called a stripper bolt..