S-91257A665 3/8"-24 x 4" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Hex Head Screws

Key Features & Benefits at a Glance

• Maximum load-bearing capacity with 150,000 psi tensile strength and Grade 8 classification for critical heavy-duty applications
• Superior corrosion resistance through zinc yellow-chromate plating, extending service life in harsh industrial environments
• Precise thread engagement with Class 2A UNF fine threads ensuring reliable, vibration-resistant connections
• Optimized torque transmission via external hex drive design and 9/16" head width for secure installation
• Enhanced durability from Rockwell C33 hardness and steel construction resisting deformation under extreme loads
• Versatile partial threading providing both gripping strength and clearance where full threading isn't required
• Regulatory compliance assurance meeting ASME B18.2.1, SAE J429, RoHS 3, and REACH standards

Professional Applications & Engineering Value

These Grade 8 hex head screws deliver exceptional engineering value in demanding applications where failure isn't an option. The 3/8"-24 UNF fine thread configuration provides superior resistance to vibrational loosening compared to coarse threads, making them ideal for heavy machinery, structural assemblies, and automotive systems. The zinc yellow-chromate plating creates a protective barrier against corrosion while maintaining electrical conductivity, crucial for grounding applications. With partial threading and 4" length, these fasteners offer optimal clamp load distribution while allowing unthreaded shank sections to function as precision pins or pivots. The 150,000 psi tensile strength ensures these screws maintain integrity under extreme static and dynamic loads, solving critical fastening challenges in construction, manufacturing, and mechanical engineering projects.

Specification Summary & Compliance

Manufactured to exacting ASME B18.2.1 specifications and SAE J429 Grade 8 requirements, these hex head screws feature precision Class 2A thread fit with 3/8"-24 UNF fine threads and minimum 1" thread length. The inch system fasteners demonstrate full compliance with RoHS 3 (2015/863/EU) restrictions on hazardous substances and REACH (EC 1907/2006) regulations regarding chemical safety. The combination of Rockwell C33 hardness and controlled manufacturing processes ensures consistent performance across production batches for reliable industrial fastening solutions.