S-91257A591 5/16"-18 x 2" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Hex Head Screws

Key Features & Benefits at a Glance

• Maximum load-bearing capacity with 150,000 psi tensile strength and Grade 8 classification for critical structural applications
• Superior corrosion resistance through zinc yellow-chromate plating, extending service life in harsh industrial environments
• Optimized torque transmission with external hex drive design ensuring secure installation and removal
• Enhanced thread engagement with UNC coarse threading providing excellent grip in various materials
• Precision manufacturing with Class 2A thread fit ensuring consistent performance and reliable assembly
• Partial threading design offering both gripping strength and clearance flexibility in assembly applications
• Industry compliance assurance meeting ASME B18.2.1 and SAE J429 standards for quality and reliability

Professional Applications & Engineering Value

This Grade 8 hex head screw delivers exceptional engineering value in demanding industrial applications where failure is not an option. The steel construction with Rockwell C33 hardness provides the perfect balance between strength and ductility, preventing brittle fracture under heavy loads. The zinc yellow-chromate plating creates a protective barrier against corrosion, making it ideal for outdoor equipment, machinery, and automotive assemblies exposed to moisture and chemicals. The 5/16"-18 UNC coarse thread ensures rapid installation and superior holding power in both soft and hard materials, while the partially threaded design allows for precise clamping force distribution. These heavy-duty screws are engineered to withstand vibration, shock loads, and extreme tension in construction, manufacturing, and transportation equipment.

Specification Summary & Compliance

This fastener features Class 2A thread fit tolerance for consistent assembly performance and meets ASME B18.2.1 and SAE J429 manufacturing specifications. The product is fully RoHS 3 (2015/863/EU) Compliant and REACH (EC 1907/2006) Compliant, ensuring environmental responsibility and regulatory adherence for global industrial applications. Dimensions include 2" length, 5/16"-18 UNC thread size, with 7/32" head height and 1/2" head width for standardized tool compatibility.