S-91670A540 1/4"-20 x 3/4" ASTM A574 Left-Hand Threaded Alloy Steel Socket Head Screws

Key Features & Benefits at a Glance

• Exceptional tensile strength of 170,000 PSI provides superior load-bearing capacity and resistance to mechanical failure in demanding applications.
• High Rockwell C37 hardness ensures excellent wear resistance and long-term durability, reducing the need for frequent replacements.
• Corrosion-resistant Black-Oxide coating on the alloy steel body protects against rust and degradation, extending service life in harsh environments.
• Precise Class 3A thread fit guarantees secure, vibration-resistant connections and reliable performance in left-hand threaded assemblies.
• Standard hex socket drive allows for easy installation and removal with common tools, minimizing assembly time and effort.
• Coarse UNC threading enables quick engagement and robust fastening, ideal for applications requiring rapid assembly or disassembly.
• Full threading along the 3/4" length offers versatile positioning and consistent clamping force across the entire fastener.

Professional Applications & Engineering Value

This left-hand thread socket head cap screw is engineered to address critical challenges in industrial settings where reverse-threading is essential to prevent loosening from counter-rotational forces. The black-oxide alloy steel construction, combined with a UNC coarse thread and Class 3A fit, delivers reliable performance in high-vibration machinery, automotive systems, and specialized equipment. Its 170,000 PSI tensile strength and Rockwell C37 hardness ensure it withstands extreme operational stresses, while the hex drive design facilitates secure tool engagement in confined spaces. Ideal for maintenance-heavy or safety-critical applications, this screw provides a durable, corrosion-resistant fastening solution that maintains integrity under demanding conditions.

Specification Summary & Compliance

This socket head cap screw features a 1/4"-20 left-hand UNC thread with a Class 3A thread fit for precise dimensional accuracy. It is manufactured in compliance with ASTM A574 specifications and meets RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental standards, ensuring it is free from hazardous substances and suitable for global industrial use.