S-91251A591 5/16"-18 x 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 thread precision with Class 3A fit provides tighter tolerances for secure, vibration-resistant assemblies in demanding environments.
• Durable black-oxide coating on alloy steel offers enhanced corrosion resistance, extending service life in industrial settings.
• High hardness rating (Rockwell C37) maintains structural integrity under heavy loads, minimizing wear and deformation.
• Partially threaded design allows for precise clamping force control, ideal for applications requiring specific grip lengths.
• Standard hex drive (1/4") enables easy installation with common tools, reducing assembly time and improving efficiency.
• Coarse UNC threads facilitate quick engagement and disassembly, streamlining maintenance and repairs.

Professional Applications & Engineering Value

These Black-Oxide Alloy Steel Socket Head Cap Screws are engineered to address critical challenges in heavy-duty machinery, automotive, and aerospace assemblies. The Class 3A thread fit ensures minimal backlash and superior clamp load retention, preventing loosening under vibration—a common issue in dynamic systems. With a 170,000 PSI tensile strength and Rockwell C37 hardness, they withstand extreme mechanical stresses without compromising integrity. The black-oxide surface treatment provides a protective layer against rust and abrasion, making them suitable for humid or corrosive environments. Ideal for partially threaded fastening in precision equipment, these screws deliver consistent performance where exact thread engagement is crucial for safety and reliability.

Specification Summary & Compliance

This product adheres to UNC coarse thread standards with a Class 3A thread fit for high precision. It meets ASTM A574 specifications for alloy steel socket head cap screws, ensuring consistent manufacturing quality. Compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, it is free from hazardous substances, supporting environmentally responsible sourcing and usage in global markets.