S-91251A100 5/16"-18 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 prolongs service life in harsh industrial environments, minimizing maintenance needs.
• Precise Class 3A thread fit provides consistent engagement and vibration resistance, enhancing assembly integrity.
• High hardness (Rockwell C37) offers excellent wear resistance, maintaining thread integrity through repeated use.
• 1/4" hex drive design allows for easy installation with standard tools, speeding up assembly processes.
• Partially threaded shank enables secure clamping without unnecessary thread engagement, ideal for precise joint control.
• Compliance with ASTM A574, RoHS 3, and REACH ensures material quality and environmental safety for global supply chain integration.

Professional Applications & Engineering Value

This Black-Oxide Alloy Steel Socket Head Cap Screw is engineered to address critical fastening challenges in demanding sectors such as heavy machinery, automotive assembly, and structural frameworks. The 5/16"-18 UNC coarse thread and Class 3A fit deliver superior grip and vibration resistance, preventing loosening under dynamic loads. The black-oxide surface treatment combats rust and corrosion, extending component life in humid or abrasive conditions. With a high tensile strength of 170,000 psi, it reliably secures high-load connections, reducing downtime and maintenance costs. Ideal for applications requiring partially threaded designs, it ensures precise clamping force distribution without compromising thread integrity, making it a trusted choice for engineers prioritizing durability and compliance.

Specification Summary & Compliance

This screw adheres to UNC coarse thread standards with a Class 3A thread fit for precise dimensional accuracy. It meets ASTM A574 specifications for alloy steel socket head cap screws, ensuring consistent material and mechanical properties. The product is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, confirming its safety for use in regulated industries and global markets.