S-91251A217 5-40 x 1 1/8" ASTM A574 Alloy Steel Socket Head Screws

Key Features & Benefits at a Glance

• Exceptional tensile strength of 170,000 psi ensures reliable performance in high-stress applications, reducing the risk of fastener failure.
• Superior corrosion resistance from the black-oxide finish extends service life in harsh industrial environments, minimizing maintenance needs.
• Precise Class 3A thread fit provides smooth assembly and secure fastening, improving installation efficiency and joint integrity.
• High Rockwell C37 hardness offers excellent wear resistance, maintaining dimensional stability under repeated loads.
• Partially threaded design allows for optimal grip and clamping force control, ideal for components requiring specific engagement lengths.
• Hex socket drive enables high-torque application with standard tools, reducing stripping and enhancing workplace safety.
• Compliance with ASTM A574, RoHS 3, and REACH ensures material consistency and environmental safety, supporting global supply chain requirements.

Professional Applications & Engineering Value

Engineered for demanding industrial settings, these 5-40 UNC Socket Head Cap Screws in black-oxide alloy steel address critical challenges like vibration loosening and corrosion. The coarse thread spacing and Class 3A thread fit facilitate quick assembly in machinery, automotive, and aerospace components, where precision and durability are paramount. The partially threaded configuration allows engineers to specify exact clamping zones, reducing stress concentration. With a 170,000 psi tensile strength and Rockwell C37 hardness, they withstand extreme operational stresses, ensuring long-term reliability in heavy-duty fastening applications while meeting strict industry standards.

Specification Summary & Compliance

This screw adheres to Class 3A thread fit tolerances for precise engagement, with UNC coarse threads in a 5-40 thread size and right-hand thread direction. Manufactured per ASTM A574 specifications, it ensures consistent quality and performance. The product is fully RoHS 3 (2015/863/EU) Compliant and REACH (EC 1907/2006) Compliant, confirming adherence to environmental and safety regulations for global industrial use.