S-91251A894 7/8"-9 x 5 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 extends service life in demanding industrial environments.
• Precise Class 3A thread fit guarantees secure, vibration-resistant connections, minimizing loosening over time.
• Robust Rockwell C37 hardness provides excellent wear resistance, maintaining integrity under repeated use.
• Convenient 3/4" hex drive allows for easy installation and removal with standard tools, saving time on assembly lines.
• Coarse UNRC threading enables quick engagement and disassembly, ideal for maintenance-heavy equipment.
• Compliance with ASTM A574, RoHS 3, and REACH ensures environmental safety and meets global regulatory standards for industrial use.

Professional Applications & Engineering Value

This black-oxide alloy steel socket head cap screw is engineered to address critical challenges in heavy machinery, automotive, and construction sectors. Its high tensile strength and Rockwell C37 hardness prevent stripping and deformation under extreme loads, while the coarse UNRC thread resists jamming in dirty or high-vibration environments. The partially threaded design concentrates clamping force where needed, reducing stress concentration. Ideal for industrial fastening in equipment requiring frequent disassembly, it combines durability with ease of maintenance, supported by ASTM A574 specifications for consistent quality.

Specification Summary & Compliance

This screw features a 7/8"-9 coarse thread with Class 3A fit for precise tolerance, a 5 1/2" length, and 3/4" hex drive. It complies with ASTM A574 for material and manufacturing standards, and meets RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations, ensuring safe use in global industrial applications.