Diameter: 8mm Shoulder Length: 25mm Overall Length: 45mm Material: Steel Finish: Plain Head Style: Socket (5mm Hex) Thread Size: 1.25mm (Coarse) Thread Length: 13mm Hardness: Class 12.9 Type: Shoulder Bolt Specifications: ISO 7379 Box of 3. 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 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.