S-91251A112 4-40 x 5/8" ASTM A574 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
• Superior corrosion resistance from Black-Oxide coating extends service life in demanding industrial environments
• Precise Class 3A thread fit provides superior engagement and vibration resistance in critical assemblies
• Optimal hardness rating (Rockwell C37) maintains thread integrity and prevents stripping during repeated installations
• Standard hex socket drive allows for high-torque installation with common tools while minimizing head protrusion
• Full threading along 5/8" length enables versatile positioning and secure fastening across various material thicknesses
• Comprehensive compliance with ASTM A574 ensures consistent quality and performance in mechanical applications

Professional Applications & Engineering Value

These 4-40 UNC thread socket head cap screws deliver critical engineering advantages where space constraints and reliability are paramount. The Black-Oxide Alloy Steel construction provides essential corrosion protection while maintaining the 170,000 psi tensile strength required for high-stress applications. The coarse thread spacing and Class 3A thread fit ensure rapid assembly with superior vibration resistance in machinery, automotive components, and precision equipment. The standard hex socket drive accommodates high torque values without cam-out, making these fasteners ideal for confined spaces where wrench clearance is limited. Engineered to prevent loosening under dynamic loads, these screws provide long-term reliability in industrial automation, manufacturing equipment, and critical mechanical assemblies.

Specification Summary & Compliance

This socket head cap screw features precision 4-40 UNC threads with Class 3A fit and coarse thread spacing, manufactured to ASTM A574 specifications for consistent dimensional accuracy and mechanical properties. The fastener meets RoHS 3 (2015/863/EU) compliance for restricted substance control and REACH (EC 1907/2006) regulations governing chemical substances. With right-hand thread direction and fully threaded design across the 5/8" length, these screws provide reliable performance in inch-system applications requiring high-strength fastening solutions.