S-91257A178 5/8"-11 x 11" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Hex Head Screws

Key Features & Benefits at a Glance

• Exceptional load-bearing capacity with 150,000 psi tensile strength, ideal for high-stress structural connections.
• Superior corrosion resistance provided by zinc yellow-chromate plating, extending service life in harsh environments.
• High hardness rating of Rockwell C33 ensures excellent wear resistance and reduced thread deformation.
• Reliable coarse threading (UNC) with Class 2A fit enables quick assembly and secure fastening in various materials.
• Optimized partial threading design provides unthreaded shank strength where maximum clamping force is required.
• External hex drive compatibility allows for high-torque installation using standard industrial tools.
• Heavy-duty Grade 8 certification guarantees consistent performance in critical mechanical applications.

Professional Applications & Engineering Value

These Grade 8 hex head screws deliver exceptional engineering value in demanding industrial environments where fastener failure is not an option. The zinc yellow-chromate plated steel construction provides superior protection against corrosion in manufacturing facilities, outdoor equipment, and marine applications. The 5/8"-11 UNC coarse thread configuration ensures rapid installation and reliable performance in structural steel connections, heavy machinery assembly, and construction applications. With partial threading maintaining full shank diameter over most of the length, these fasteners provide maximum resistance to shear forces while concentrating thread engagement where clamping force is critical. The external hex drive design accommodates high torque requirements without stripping, making them ideal for maintenance operations and production line applications where reliability and speed are paramount.

Specification Summary & Compliance

Manufactured to precise Class 2A thread fit tolerances with 5/8"-11 UNC coarse threading and partial threading extending 1 3/4" minimum. These Grade 8 hex head screws comply with ASME B18.2.1 and SAE J429 specifications, ensuring dimensional accuracy and mechanical properties. The fasteners are fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations, making them suitable for global industrial supply chains and environmentally conscious manufacturing operations.