S-91257A836 5/8"-18 x 8" 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 provided by zinc yellow-chromate plating, extending service life in harsh environments
• Precise thread engagement with Class 2A UNF fine threads ensuring secure fastening and vibration resistance
• Optimized torque transmission through external hex drive design for easy installation with standard tools
• Enhanced durability from Rockwell C33 hardness, maintaining structural integrity under repeated loads
• Versatile partial threading allowing for both clamping and alignment functions in assembly operations
• Industry-standard compliance meeting ASME B18.2.1 and SAE J429 specifications for guaranteed interchangeability

Professional Applications & Engineering Value

These Grade 8 hex head screws deliver critical engineering solutions for heavy machinery, structural frameworks, and industrial equipment where high tensile strength and reliable fastening are paramount. 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 offers dual functionality - the threaded portion secures components while the unthreaded shank maintains precise alignment in bolted connections. With external hex drive compatibility, these fasteners enable efficient installation and maintenance using standard industrial tools, reducing assembly time and labor costs in manufacturing, construction, and equipment maintenance applications.

Specification Summary & Compliance

Manufactured to exacting Class 2A thread fit tolerances with UNF fine thread profile (18 TPI) ensuring precise engagement and interchangeability. These 8-inch hex head screws comply with ASME B18.2.1 dimensional standards and SAE J429 material specifications for Grade 8 fasteners. The inch system measurements, including the 15/16" head width and 1 3/4" minimum thread length, maintain consistency with North American industrial standards. The steel construction with Rockwell C33 hardness verification ensures mechanical properties meet the rigorous demands of heavy-duty applications while the zinc yellow-chromate finish provides environmental protection without compromising dimensional accuracy.