S-91259A626 5/16"-18 ASME B18.3, ASTM A574 Shoulder Screws

Key Features & Benefits at a Glance

• Exceptional Load-Bearing Capability: With a tensile strength of 140,000 psi and minimum shear strength of 84,000 psi, this shoulder screw reliably handles high-stress applications without failure.
• Precision Thread Fit for Secure Assembly: Class 3A thread fit ensures tight, vibration-resistant connections, reducing the risk of loosening in dynamic environments.
• Enhanced Corrosion Resistance: The black oxide finish provides a durable protective layer, extending service life in humid or mildly corrosive industrial settings.
• Superior Wear Resistance and Durability: Made from alloy steel with Rockwell C32 hardness, it offers excellent resistance to wear and deformation under repeated use.
• Accurate Shoulder Alignment: Tight shoulder diameter and length tolerances ensure precise component positioning, minimizing misalignment in machinery assemblies.
• Easy Installation and Removal: The knurled socket head with 3/16" hex drive allows for quick, secure tool engagement, speeding up maintenance and assembly processes.
• Broad Regulatory Compliance: Meets ASME B18.3, RoHS 3, and REACH standards, ensuring safety and environmental responsibility for global supply chains.

Professional Applications & Engineering Value

This alloy steel shoulder screw is engineered to address critical alignment and strength requirements in precision industrial applications. The 5/16"-18 UNC coarse thread with Class 3A fit provides reliable fastening in high-vibration environments, such as robotics, automotive assemblies, and conveyor systems, where loosening can lead to operational failures. The 1-1/4" shoulder length acts as a precise pivot or spacer, ensuring components like gears and bearings maintain exact positioning without shimming. Combined with the black oxide finish, it resists corrosion from oils and moisture, reducing maintenance needs. Its high tensile and shear strength makes it ideal for heavy-duty machinery, supporting prolonged use without compromising integrity or performance.

Specification Summary & Compliance

This shoulder screw adheres to ASME B18.3 specifications, with a Class 3A thread fit for precise UNC threading and standard shoulder dimensions (e.g., shoulder diameter tolerance of -0.004" to -0.002" and length tolerance of -0.005" to 0.005"). It is manufactured from alloy steel per ASTM A574, ensuring consistent quality. Compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006), it meets environmental and safety regulations for hazardous substance restrictions.