S-91251A543 1/4"-20 x 1 3/8" ASTM A574 Alloy Steel Socket Head Screws

Key Features & Benefits at a Glance

• Exceptional tensile strength of 170,000 psi ensures reliable performance under high-stress conditions, reducing the risk of fastener failure in demanding applications.
• Superior corrosion resistance provided by the black-oxide finish extends service life and maintains integrity in harsh industrial environments.
• Precise Class 3A thread fit guarantees secure, vibration-resistant connections, minimizing loosening and improving assembly reliability.
• High hardness rating (Rockwell C37) enhances wear resistance, allowing for repeated use without degradation of the socket or threads.
• Standard hex drive (3/16") offers easy installation and removal with common tools, speeding up maintenance and reducing labor time.
• Full threading enables consistent clamping force along the entire length, ideal for applications requiring uniform pressure distribution.
• Compliance with ASTM A574, RoHS 3, and REACH ensures adherence to strict quality and environmental standards, providing peace of mind for regulated industries.

Professional Applications & Engineering Value

These black-oxide alloy steel socket head cap screws are engineered to address common industrial challenges such as vibration-induced loosening, corrosion in exposed settings, and the need for high clamping force. The UNRC coarse thread and Class 3A fit provide excellent engagement in a variety of materials, reducing the risk of cross-threading and ensuring stable connections in machinery, automotive assemblies, and heavy equipment. The 170,000 psi tensile strength and Rockwell C37 hardness make them suitable for high-load applications, while the black-oxide surface treatment offers added protection against rust, extending service life and reducing maintenance costs in demanding environments like manufacturing plants and outdoor installations.

Specification Summary & Compliance

This 1/4"-20 socket head cap screw features a right-hand thread direction with coarse UNRC threading and Class 3A thread fit for precise dimensional accuracy. It meets ASTM A574 specifications for high-strength alloy steel fasteners and is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, ensuring environmental safety and material reliability in industrial use.