S-91257A710 7/16"-20 x 4 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 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 torque transmission via external hex head design that prevents tool slippage during installation
• Enhanced durability from Rockwell C33 hardness that maintains fastener integrity under repeated stress
• Versatile partial threading allowing both clamping and alignment functions in heavy machinery assemblies
• Regulatory compliance assurance meeting ASME, SAE, RoHS 3 and REACH standards for global industrial use

Professional Applications & Engineering Value

Engineered for heavy-duty industrial applications, these Grade 8 hex head screws solve critical fastening challenges in construction equipment, machinery frames, and structural assemblies. The 7/16"-20 UNF fine threading provides superior resistance to vibrational loosening compared to coarse threads, while the partial threading design allows unthreaded shank sections to function as precision alignment pins. The zinc yellow-chromate plating creates a protective barrier against corrosion in outdoor or high-moisture environments, significantly extending service life. With 4 1/2" length and external hex drive, these fasteners deliver optimal clamping force distribution across thick materials, making them ideal for demanding applications where joint integrity is paramount.

Specification Summary & Compliance

Manufactured to Class 2A thread fit tolerances with UNF (Unified National Fine) thread form ensuring precise engagement. Complies with ASME B18.2.1 dimensional standards and SAE J429 Grade 8 mechanical properties. Meets RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental compliance requirements. Thread specifications include 7/16"-20 fine pitch with 1 1/8" minimum thread length and right-hand thread direction.