S-91257A435 5/16"-18 x 8" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Hex Head Screws

Key Features & Benefits at a Glance

• Maximum Load-Bearing Capacity: Grade 8 classification with 150,000 psi tensile strength ensures reliable performance in high-stress industrial applications
• Superior Corrosion Protection: Zinc yellow-chromate plating provides enhanced resistance to rust and environmental degradation
• Optimized Thread Engagement: Class 2A UNC coarse threads offer easier assembly and better vibration resistance in demanding conditions
• Enhanced Durability: Rockwell C33 hardness rating maintains structural integrity under repeated stress and heavy loads
• Secure Fastening Control: External hex drive with 1/2" head width allows for high-torque installation using standard tools
• Versatile Application Design: Partial threading with 1-1/8" minimum thread length provides both gripping strength and clearance flexibility
• Industry Standard Compliance: Meets ASME B18.2.1 and SAE J429 specifications for guaranteed quality and interchangeability

Professional Applications & Engineering Value

Engineered for heavy-duty industrial applications, these Grade 8 hex head screws deliver exceptional performance in construction, machinery assembly, and structural frameworks where vibration resistance and high tensile strength are critical. The zinc yellow-chromate plating creates a protective barrier against corrosive environments, extending service life in outdoor or harsh conditions. The UNC coarse thread design ensures rapid installation and superior holding power in steel-to-steel connections, while the partial threading configuration provides optimal stress distribution. These 5/16"-18 x 8" hex screws with external hex drive accommodate high torque requirements, making them ideal for critical joints in manufacturing equipment, transportation systems, and infrastructure projects where failure is not an option.

Specification Summary & Compliance

This Grade 8 hex head screw features precise Class 2A thread fit with 5/16"-18 UNC coarse thread specifications and right-hand threading. Manufacturing complies with ASME B18.2.1 and SAE J429 standards, ensuring dimensional accuracy and mechanical properties. The fastener maintains 150,000 psi tensile strength and Rockwell C33 hardness throughout its 8" length with partial threading. The zinc yellow-chromate finish provides corrosion resistance while meeting industry requirements for heavy-duty applications.