S-91251A487 5/8"-18 x 3 1/2" 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 on alloy steel, extending service life in demanding industrial environments.
• Precision Class 3A thread fit provides tight, secure fastening with minimal play, ideal for applications requiring exact alignment.
• Fine UNRF threads offer improved vibration resistance and better load distribution compared to coarse threads.
• Partially threaded design allows for controlled clamping force and easier assembly in specific mounting scenarios.
• 1/2" hex drive socket head enables high-torque installation with standard tools, preventing stripping and ensuring consistent tightness.
• Compliance with ASTM A574, RoHS 3, and REACH guarantees material consistency, environmental safety, and regulatory acceptance.

Professional Applications & Engineering Value

Engineered for heavy-duty industrial applications, these black-oxide alloy steel socket head cap screws address critical challenges in machinery assembly, automotive systems, and structural frameworks. The UNRF fine thread configuration enhances fatigue resistance under dynamic loads, while the Class 3A thread fit ensures precise engagement in tapped holes, minimizing loosening from vibration. The partially threaded rod type provides optimal grip length for components requiring focused clamping pressure without unnecessary thread engagement. With a Rockwell C37 hardness and robust 170,000 psi tensile strength, these screws deliver long-term reliability in high-torque and high-stress environments, reducing maintenance intervals and downtime.

Specification Summary & Compliance

This socket head cap screw features a 5/8"-18 UNRF thread with Class 3A precision tolerance for accurate fit, a 3 1/2" length, and fine thread spacing. It meets ASTM A574 specifications for high-strength alloy steel fasteners, ensuring consistent mechanical properties. The product is fully RoHS 3 (2015/863/EU) Compliant and REACH (EC 1907/2006) Compliant, adhering to environmental and safety regulations for industrial use.