Shoulder Screws

Imperial socket head shoulder screws, also known as precision shoulder screws, are high-precision and high-strength fasteners manufactured in accordance with ASME B18.3 and BS 4168 standards. They feature a smooth, precision-ground shoulder and a threaded section, providing accurate location, axial retention, and resistance to shear forces in one component. These screws are widely used in export-oriented machinery and imperial-standard equipment.
 

Applications
They are mainly applied in precision molds, injection molds, and stamping dies, serving as limit pins, positioning components, and ejector retainers to ensure stable operation and high dimensional accuracy. They are also commonly used in automated machinery, machine tools, hydraulic systems, textile equipment, automotive tooling, and aerospace components. Due to their imperial dimensions and robust performance, they are ideal for overseas equipment assembly and high-load, high-vibration working environments.
 

Grades & Materials
Imperial shoulder screws are mostly made of high-strength alloy steel, with ASTM A574 being the most common specification, equivalent to metric Grade 12.9.
- Grade 12.9: Produced from SCM435 alloy steel, with quenching and tempering treatment, hardness HRC 39–44. It offers excellent tensile strength and fatigue resistance, suitable for high-precision molds and heavy-duty equipment.
- Stainless steel 304/316: Provides strong corrosion resistance, used in food processing, medical devices, marine equipment, and other environments requiring rust protection.
Thread precision is commonly classified as 2A or 3A, with 3A representing tighter tolerances for high-end precision assemblies.
Combining positioning, fastening, and limiting functions, imperial shoulder screws are essential components for export molds and imperial-standard mechanical systems, where material grade and precision directly affect equipment reliability, service life, and operational safety.