S-91251A489 5/8"-18 x 4 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 industrial applications, reducing the risk of fastener failure.
• Class 3A thread fit provides superior precision and tighter tolerances for secure, vibration-resistant assemblies in critical machinery.
• Black-oxide coating on alloy steel offers enhanced corrosion resistance and durability, extending service life in demanding environments.
• Partially threaded design with fine UNRF threads allows for precise clamping force control and improved engagement in tapped holes.
• Hex socket drive (1/2") enables high-torque installation with standard tools, facilitating efficient assembly and maintenance.
• Compliance with ASTM A574, RoHS 3, and REACH ensures material consistency, environmental safety, and global regulatory acceptance for your projects.
• Rockwell C37 hardness balances toughness and machinability, resisting wear and deformation under heavy loads.

Professional Applications & Engineering Value

This black-oxide alloy steel socket head cap screw is engineered to address common industrial challenges such as vibration loosening, corrosion, and high tensile demands. The fine UNRF thread (5/8"-18) and Class 3A fit provide exceptional thread engagement and clamping force, making it ideal for precision equipment, automotive assemblies, and heavy machinery where reliability is critical. The partially threaded rod type allows for targeted fastening without unnecessary thread contact, reducing stress concentration. With a Rockwell C37 hardness and robust 170,000 psi tensile strength, it withstands dynamic loads and harsh conditions, ensuring long-term performance in construction, aerospace, and manufacturing applications.

Specification Summary & Compliance

This socket head cap screw features a Class 3A thread fit with precise UNRF fine threads (5/8"-18), ensuring tight tolerances and reliable performance. It is manufactured in accordance with ASTM A574 specifications for high-strength alloy steel socket head cap screws. The product is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, confirming its adherence to environmental and safety standards for industrial use.