S-91247A807 5/8"-11 x 3 1/4" ASME B18.2.1, SAE J429 Medium-Strength Grade 5 Steel Hex Head Screws

Key Features & Benefits at a Glance

• Exceptional load-bearing capacity with 120,000 psi tensile strength, ideal for heavy-duty structural and machinery applications
• Superior corrosion resistance from zinc plating, extending service life in harsh industrial environments
• Reliable thread engagement with Class 2A fit and UNC coarse threading, preventing cross-threading and ensuring consistent clamping force
• Optimized torque transmission through the external hex drive and 15/16" head width, enabling secure installation with standard tools
• Enhanced durability from Rockwell C25 hardness, maintaining structural integrity under vibration and dynamic loads
• Controlled thread engagement with partial threading, providing unthreaded shank for precise shear load distribution
• Industry-standard compatibility meeting ASME B18.2.1 specifications, ensuring interchangeability and engineering consistency

Professional Applications & Engineering Value

This Grade 5 steel hex head screw delivers critical performance in demanding industrial fastening scenarios where failure is not an option. The 5/8"-11 UNC coarse thread configuration combined with Class 2A thread fit provides rapid installation while maintaining precise tolerances, significantly reducing assembly time in construction and machinery applications. The zinc plated finish creates a sacrificial barrier against oxidation, making these external hex drive fasteners suitable for outdoor equipment, structural steel connections, and manufacturing environments where moisture exposure is common. The partially threaded design concentrates the thread engagement where needed most, preventing stress concentration in the shank area and providing superior resistance to vibrational loosening in dynamic load conditions.

Specification Summary & Compliance

Manufactured to exacting inch system dimensions with 3 1/4" length and 1 1/2" minimum thread length. Thread specifications include 5/8"-11 UNC coarse thread with Class 2A fit ensuring proper clearance and engagement. Complies with ASME B18.2.1 and SAE J429 Grade 5 standards for dimensional accuracy and mechanical properties. Meets environmental regulations including RoHS 3 (2015/863/EU) compliance and REACH (EC 1907/2006) requirements for hazardous substance restrictions.