S-91251A888 7/8"-9 x 4" 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 secure, vibration-resistant connections, enhancing assembly integrity and reducing loosening over time.
• High hardness (Rockwell C37) offers excellent wear resistance, maintaining thread integrity through repeated use and disassembly.
• 3/4" hex drive design allows for high-torque installation with standard tools, speeding up assembly and reducing labor costs.
• Partially threaded shank enables optimal clamping force distribution, ideal for applications requiring precise joint compression.
• Compliance with ASTM A574, RoHS 3, and REACH ensures material consistency and environmental safety, meeting global regulatory standards.

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. The UNRC coarse thread and Class 3A fit provide superior resistance to vibrational loosening, a common issue in dynamic load environments. With a 1 5/16" head diameter and standard socket head profile, it ensures even load distribution and easy access in confined spaces. The black-oxide surface treatment not only enhances corrosion resistance but also reduces galling during installation, prolonging tool life. Ideal for high-torque applications, this screw’s partially threaded design minimizes stress concentration, making it a reliable choice for structural assemblies and equipment requiring repeated maintenance.

Specification Summary & Compliance

This socket head cap screw features a 7/8"-9 UNRC coarse thread with Class 3A thread fit for precise dimensional accuracy. It is manufactured in accordance with ASTM A574 specifications, ensuring consistent mechanical properties. 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.