S-91571A421 5/8"-11 x 5 1/4" ASME B18.2.6, ASTM A325, ASTM F3125 Medium-Strength Steel Heavy Hex Head Screws for Structural Applications

Key Features & Benefits at a Glance

• Exceptional structural integrity with Grade A325 classification and 120,000 psi tensile strength for reliable performance in demanding applications
• Superior durability achieved through Rockwell C19 hardness and steel construction, ensuring long service life under heavy loads
• Optimized installation efficiency with external hex drive and coarse UNC threading that resists vibration loosening
• Precise thread engagement with Class 2A fit providing consistent clamping force and reduced risk of cross-threading
• Versatile partial threading design offering both threaded engagement and smooth shank sections for optimal load distribution
• Full regulatory compliance with RoHS 3 and REACH environmental standards for global industrial applications
• Standardized dimensions ensuring compatibility with existing tooling and mating components across various assemblies

Professional Applications & Engineering Value

These Grade A325 hex head screws deliver critical engineering solutions for structural steel connections, heavy machinery assembly, and construction frameworks where failure is not an option. The partially threaded design creates an optimal balance between the threaded portion for secure fastening and the smooth shank for bearing applications, preventing stress concentration at thread roots. With coarse UNC threading and Class 2A thread fit, these screws provide superior resistance to vibration-induced loosening while maintaining easy installation in structural steel members. The external hex drive configuration allows for high torque application using standard tools, making them ideal for critical connections in bridges, buildings, and industrial equipment where 120,000 psi tensile strength ensures structural integrity under extreme loads.

Specification Summary & Compliance

Manufactured to exacting ASME B18.2.6 dimensional standards with Class 2A thread fit precision. These structural hex head screws comply with ASTM A325 and ASTM F3125 material and performance specifications for structural bolting applications. Full compliance with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations ensures suitability for global industrial markets. The 5/8"-11 UNC coarse thread configuration with 5 1/4" length and 4" grip length provides standardized dimensions for predictable performance across applications.