S-91257A491 1/2"-20 x 7" 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 Grade 8 classification and 150,000 psi tensile strength for critical structural applications
• Superior corrosion protection through zinc yellow-chromate plating that withstands harsh industrial environments
• Precise thread engagement with Class 2A UNF fine threads ensuring reliable fastening in high-vibration settings
• Optimized strength-to-weight ratio through partial threading design that concentrates material where needed most
• Enhanced installation efficiency with external hex drive and 3/4" head width for secure tool engagement
• Long-term reliability backed by Rockwell C33 hardness that maintains performance under repeated stress
• Regulatory compliance assurance meeting ASME B18.2.1, RoHS 3, and REACH standards for global project specifications

Professional Applications & Engineering Value

Engineered for heavy-duty industrial applications, these Grade 8 hex head screws deliver exceptional performance where failure is not an option. The 1/2"-20 UNF fine threading provides superior resistance to vibration loosening in machinery, construction equipment, and structural assemblies. The zinc yellow-chromate plating creates a robust barrier against corrosion in demanding environments, from manufacturing facilities to outdoor installations. With partial threading concentrating the 150,000 psi tensile strength precisely where needed, these 7-inch fasteners eliminate unnecessary weight while maintaining critical clamping force. The external hex drive design ensures secure tool engagement during high-torque installation, making them ideal for maintenance operations and production line applications requiring reliable, repeatable fastening solutions.

Specification Summary & Compliance

This hex head screw features precise Class 2A thread fit with UNF fine thread spacing (1/2"-20) and minimum thread length of 1-1/2". Manufactured to ASME B18.2.1 specifications where identified by SAE J429 standards, ensuring dimensional accuracy and interchangeability. The fastener is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations, meeting the latest international requirements for hazardous substance restrictions.