S-91257A589 5/16"-18 x 1 3/4" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Hex Head Screws

Key Features & Benefits at a Glance

• Maximum Load 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 - UNC coarse threading with Class 2A fit guarantees secure fastening and vibration resistance
• Enhanced Durability - Rockwell C33 hardness maintains structural integrity under repeated stress and heavy loads
• Easy Installation & Removal - External hex drive with 1/2" head width allows for standard wrench access and high torque application
• Versatile Fastening Solution - Partially threaded design provides both gripping strength and clearance where needed
• Industry Compliance Assurance - Meets critical standards for quality, safety, and environmental regulations

Professional Applications & Engineering Value

Engineered for demanding industrial environments, these Grade 8 hex head screws deliver exceptional performance in heavy machinery, structural steel connections, and high-vibration equipment. The 5/16"-18 UNC coarse thread configuration ensures rapid installation and superior holding power in various materials, while the zinc yellow-chromate plating provides critical corrosion resistance in outdoor or harsh chemical environments. The partially threaded design allows for precise clamping force distribution, making these steel fasteners ideal for applications requiring both secure engagement and proper alignment. With their external hex drive and robust construction, they withstand extreme torque requirements in automotive, construction, and manufacturing applications where failure is not an option.

Specification Summary & Compliance

This Grade 8 hex head screw features precise Class 2A thread fit tolerances with 5/16"-18 UNC coarse threading and right-hand thread direction. Manufacturing complies with ASME B18.2.1 and SAE J429 specifications, ensuring dimensional accuracy and performance reliability. The fastener meets RoHS 3 (2015/863/EU) compliance for hazardous substance restrictions and REACH (EC 1907/2006) standards for chemical safety, making it suitable for global industrial applications requiring stringent regulatory adherence.