S-91251A589 5/16"-18 x 1 3/4" 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, reducing the risk of fastener failure in demanding applications.
• Superior corrosion resistance provided by the black-oxide finish on alloy steel, extending service life in harsh industrial environments.
• Precise Class 3A thread fit guarantees secure, vibration-resistant assemblies with minimal risk of loosening.
• High Rockwell C37 hardness offers excellent wear resistance, maintaining thread integrity through repeated use.
• 1/4" hex drive socket head allows for high-torque installation and easy access in confined spaces.
• Partially threaded design provides optimal clamping force on specific joint areas without unnecessary threading.
• Compliance with ASTM A574, RoHS 3, and REACH ensures material quality and environmental safety for global supply chains.

Professional Applications & Engineering Value

This Black-Oxide Alloy Steel Socket Head Cap Screw is engineered to solve critical fastening challenges in heavy machinery, automotive assemblies, and precision equipment. The coarse UNC thread and Class 3A fit enable quick, secure installation while resisting vibration-induced loosening—a common pain point in dynamic load environments. The alloy steel construction combined with 170,000 psi tensile strength provides a reliable solution for high-stress applications where fastener integrity is non-negotiable. Its partially threaded shank concentrates clamping force exactly where needed, preventing joint slippage and improving overall assembly stability. The black-oxide surface treatment not only enhances corrosion resistance but also reduces galling during installation, extending tool life and maintenance intervals.

Specification Summary & Compliance

This screw features a 5/16"-18 UNC coarse thread with Class 3A precision fit and a minimum thread length of 1 1/8". It is manufactured in accordance with ASTM A574 specifications, ensuring consistent quality and performance. The product is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, meeting international standards for restricted substances and environmental safety.