S-91257A832 5/8"-18 x 4 1/2" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Hex Head Screws

Key Features & Benefits at a Glance

• Exceptional load-bearing capability with 150,000 psi tensile strength for reliable performance in high-stress applications
• Superior corrosion resistance through zinc yellow-chromate plating that protects against harsh industrial environments
• Precise thread engagement with Class 2A fit and UNF fine threads ensuring secure fastening and vibration resistance
• Maximum durability from Rockwell C33 hardness and Grade 8 classification for long service life
• Optimized torque transmission through external hex drive design and 15/16" head width for easy installation
• Versatile partial threading allowing both threaded and unthreaded sections for specific clamping requirements
• 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 critical engineering solutions for heavy machinery, structural assemblies, and industrial equipment where failure is not an option. The 5/8"-18 UNF fine thread configuration provides superior resistance to vibrational loosening compared to coarse threads, while the zinc yellow-chromate plating creates a robust barrier against corrosion in demanding environments. The partially threaded design allows for precise clamping force distribution, making these industrial strength fasteners ideal for applications requiring both threaded engagement and smooth shank benefits. With 150,000 psi tensile strength and Rockwell C33 hardness, these screws maintain integrity under extreme mechanical stress, ensuring reliable performance in construction, automotive, and manufacturing applications where safety and durability are paramount.

Specification Summary & Compliance

This hex head screw features precise Class 2A thread fit tolerances with 5/8"-18 UNF fine threading and 1 1/2" minimum thread length. Manufactured to ASME B18.2.1 and SAE J429 Grade 8 specifications, the fastener ensures dimensional accuracy and mechanical reliability. Compliance with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations guarantees environmental safety and restricted substance adherence for global industrial applications.