S-91251A307 7/8"-14 x 2 1/4" ASTM A574 Alloy Steel Socket Head Screws

Key Features & Benefits at a Glance

• Exceptional tensile strength of 170,000 psi ensures reliable performance under extreme loads, minimizing the risk of fastener failure in critical applications.
• Superior thread precision with Class 3A UNRF fine threads provides a tighter, more secure fit, enhancing vibration resistance and joint integrity.
• Enhanced corrosion resistance from the black-oxide coating on alloy steel prolongs service life in harsh industrial environments, reducing maintenance needs.
• High hardness rating of Rockwell C37 offers excellent wear resistance, maintaining dimensional stability and thread integrity through repeated use.
• Optimized for high-torque applications with a 3/4" hex drive and standard socket head profile, allowing for easy installation and removal with common tools.
• Full threading along the 2 1/4" length ensures uniform load distribution and maximum grip strength across the entire fastened joint.
• Compliance with industry standards including ASTM A574 guarantees consistent quality and performance, backed by RoHS 3 and REACH environmental regulations.

Professional Applications & Engineering Value

This black-oxide alloy steel socket head cap screw is engineered to address common challenges in heavy machinery, automotive assembly, and structural frameworks where vibration loosening and high stress are prevalent. The UNRF Class 3A fine thread design delivers precise engagement, reducing the likelihood of cross-threading and ensuring a leak-proof seal in pressurized systems. Its high tensile strength and Rockwell C37 hardness make it ideal for applications requiring repeated disassembly without thread degradation, such as in mold bases, hydraulic fixtures, and aerospace components. The black-oxide surface treatment provides a durable barrier against rust and chemical exposure, extending service life in outdoor or corrosive environments while maintaining consistent torque performance.

Specification Summary & Compliance

This socket head cap screw features a 7/8"-14 UNRF fine thread with Class 3A fit, ensuring tight tolerances and superior thread engagement for precision assemblies. Manufactured in compliance with ASTM A574 specifications, it meets rigorous mechanical and dimensional standards. The product is fully RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) compliant, adhering to environmental and safety regulations for use in global industrial markets. The fully threaded, right-hand design and standardized dimensions guarantee interchangeability and reliability in demanding engineering applications.