S-91670A585 5/16"-18 x 1 1/4" 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 in high-stress applications, reducing the risk of fastener failure.
• Left-hand threading provides secure fastening in applications where right-hand rotation could cause loosening, ideal for rotating machinery and specialized equipment.
• Black-oxide coating on alloy steel offers superior corrosion resistance and a durable, non-reflective finish for extended service life.
• Class 3A thread fit delivers precise, tight tolerances for improved assembly accuracy and vibration resistance in demanding environments.
• Fully threaded design allows for maximum grip and adjustability along the entire length, enhancing versatility in various mounting scenarios.
• Rockwell C37 hardness ensures high durability and wear resistance, maintaining integrity under repeated use and heavy loads.
• Hex socket drive enables easy installation with standard tools, reducing assembly time and improving efficiency in industrial settings.

Professional Applications & Engineering Value

This left-hand thread socket head cap screw is engineered to address critical challenges in industrial and mechanical systems where reverse-thread fastening is essential. Made from black-oxide alloy steel, it combats corrosion and wear in harsh environments, while the UNC coarse threading and Class 3A fit provide secure, vibration-resistant connections in machinery, automotive assemblies, and heavy equipment. The fully threaded design ensures consistent clamping force, making it ideal for applications requiring precise alignment and stability. By integrating high tensile strength and compliance with industry standards, this fastener minimizes maintenance needs and enhances operational reliability in left-hand fastening scenarios.

Specification Summary & Compliance

This screw adheres to inch system measurements with a 5/16"-18 UNC thread size and Class 3A thread fit for precise dimensional accuracy. It meets ASTM A574 specifications for high-strength alloy steel socket head cap screws, ensuring consistent manufacturing quality. Additionally, it is compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, supporting environmental safety and industrial reliability.