S-91670A546 1/4"-20 x 1 1/2" ASTM A574 Left-Hand Threaded 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.
• Left-hand UNC thread design provides secure fastening in applications where standard right-hand threads may loosen due to rotational forces, enhancing operational safety.
• Black-oxide coating on alloy steel offers superior corrosion resistance, extending the screw's service life in harsh industrial environments.
• Class 3A thread fit guarantees precise thread engagement and consistent clamping force, minimizing vibration-induced loosening.
• Hex socket drive (3/16") allows for high-torque installation with standard tools, facilitating efficient assembly and maintenance.
• Full-threaded rod design ensures uniform load distribution along the entire length, improving joint integrity in critical assemblies.
• Compliance with ASTM A574, RoHS 3, and REACH ensures material quality and environmental safety, meeting rigorous industry and regulatory standards.

Professional Applications & Engineering Value

This Black-Oxide Alloy Steel Socket Head Cap Screw is engineered to address common challenges in industrial settings, such as vibration resistance and corrosion. The left-hand UNC 1/4"-20 coarse threads are specifically designed for applications where reverse rotation is a concern, such as in machinery with counter-clockwise moving parts, preventing unintentional loosening. The alloy steel construction combined with a Rockwell C37 hardness provides durability against wear and fatigue, making it ideal for heavy-duty equipment, automotive assemblies, and aerospace components. Its fully threaded and Class 3A fit ensures tight tolerances, reducing the need for frequent retightening and maintenance, thereby lowering downtime and operational costs in industrial fastener systems.

Specification Summary & Compliance

This screw features precise Class 3A thread fit with UNC coarse threads and a length of 1 1/2 inches, ensuring dimensional accuracy per inch system standards. It complies with ASTM A574 for material and manufacturing quality, and meets RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations for environmental safety, confirming its suitability for global industrial use without hazardous substances.