S-91286A608 5/16"-18 x 1/2" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Hex Head Screws

Key Features & Benefits at a Glance

• Maximum load-bearing capability with 150,000 psi tensile strength and Grade 8 classification for critical structural applications
• Superior corrosion protection through zinc-flake coating, extending service life in harsh industrial environments
• Enhanced installation efficiency with external hex drive design providing secure tool engagement and high torque transmission
• Reliable thread engagement with Class 2A thread fit ensuring consistent assembly performance and vibration resistance
• Optimized for heavy machinery featuring coarse UNC threads that resist loosening under dynamic loads and vibration
• Consistent mechanical properties with Rockwell C33 hardness maintaining dimensional stability under extreme pressure
• Full-threaded design offering maximum grip length and uniform stress distribution across the entire fastener

Professional Applications & Engineering Value

These Grade 8 hex head screws deliver exceptional engineering value in demanding industrial settings where fastener failure is not an option. The zinc-flake coated steel construction provides superior corrosion resistance, making these 5/16"-18 UNC fasteners ideal for outdoor equipment, heavy machinery, and structural assemblies exposed to environmental challenges. The external hex drive design ensures positive tool engagement even in high-torque applications, while the coarse thread spacing maintains holding power in materials prone to vibration-induced loosening. With fully threaded construction, these screws distribute clamping force evenly across the entire engagement length, preventing stress concentration points that can lead to material fatigue. Engineered to meet the rigorous demands of construction, automotive, and industrial manufacturing applications, these high-strength fasteners provide reliable performance where safety and durability are paramount concerns.

Specification Summary & Compliance

This Grade 8 hex head screw features precise Class 2A thread fit tolerance with 5/16"-18 UNC coarse thread configuration in right-hand orientation. Manufactured to exacting standards including ASME B18.2.1 and SAE J429 specifications, ensuring dimensional accuracy and mechanical performance. The fastener demonstrates full compliance with environmental regulations including RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) requirements. With a length of 1/2" and complete threading, this inch-system fastener maintains consistent quality for industrial applications requiring reliable fastening solutions.