S-91211A217 5/8"-11 x 3 1/2" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Thread-Locking Hex Head Screws

Key Features & Benefits at a Glance

• Superior vibration resistance with nylon patch thread locker that maintains locking performance from -55° to 250°F
• Exceptional load-bearing capability with Grade 8 strength rating and 150,000 psi tensile strength for heavy-duty applications
• Enhanced corrosion protection through zinc yellow-chromate plating that extends service life in demanding environments
• Reliable installation and removal with external hex drive design providing secure tool engagement and torque transfer
• Optimized thread engagement through Class 2A thread fit ensuring consistent performance and proper fastening
• Versatile partial threading allowing for both clamping force and clearance in various assembly configurations
• Industry-standard compliance meeting ASME B18.2.1 and SAE J429 specifications for quality assurance

Professional Applications & Engineering Value

This Grade 8 hex head screw with 5/8"-11 UNC coarse threading delivers exceptional engineering value in demanding industrial environments. The zinc yellow-chromate plated steel construction provides superior corrosion resistance while maintaining the Rockwell C33 hardness required for high-stress applications. The innovative nylon patch thread locking technology effectively prevents loosening under extreme vibration conditions, making these partially threaded fasteners ideal for heavy machinery, construction equipment, and automotive assemblies where reliability is critical. The external hex drive design ensures secure tool engagement during installation, while the 3 1/2" length provides ample engagement for structural connections requiring maximum clamping force and vibration resistance.

Specification Summary & Compliance

This high-strength fastener features Class 2A thread fit precision with 5/8"-11 UNC coarse threads and partial threading configuration. Manufactured to exacting ASME B18.2.1 and SAE J429 specifications, ensuring dimensional accuracy and performance reliability. The Grade 8 strength classification guarantees 150,000 psi tensile strength and Rockwell C33 hardness for demanding applications. The nylon patch thread locker maintains effectiveness across a wide temperature range from -55° to 250°F, providing consistent vibration resistance in varied operating conditions.