S-91670A587 5/16"-18 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 in high-stress applications, reducing the risk of fastener failure
• Durable black-oxide coating on alloy steel provides superior corrosion resistance and extends service life in demanding environments
• Precision Class 3A thread fit delivers superior engagement and vibration resistance for secure left-hand fastening applications
• Standard hex socket drive allows for easy installation with common tools while providing high torque capability
• Rockwell C37 hardness rating maintains structural integrity under heavy loads and repeated use
• Fully threaded design ensures maximum grip length and consistent holding power across the entire fastener
• Comprehensive compliance with ASTM A574, RoHS 3, and REACH standards guarantees quality and environmental responsibility

Professional Applications & Engineering Value

This left hand thread socket head cap screw addresses critical engineering challenges in industrial settings where reverse-thread applications prevent loosening from rotational forces. The black-oxide alloy steel construction provides exceptional durability against wear and environmental exposure, while the UNC coarse thread pattern ensures rapid installation and superior holding power in various materials. Engineered with a Class 3A thread fit, this fastener delivers precision engagement that resists vibration-induced failure in machinery, automotive assemblies, and heavy equipment. The combination of 170,000 psi tensile strength and Rockwell C37 hardness makes it ideal for applications requiring reliable left-hand fastening solutions that maintain integrity under extreme mechanical stress and repeated loading cycles.

Specification Summary & Compliance

This socket head cap screw features precise 5/16"-18 UNC coarse threads with Class 3A fit for superior dimensional accuracy and engagement. Manufactured to ASTM A574 specifications for high-strength alloy steel socket head cap screws, ensuring consistent quality and performance. The product is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations, confirming its suitability for use in regulated industries and international markets.