S-91257A931 7/8"-9 x 10" 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 a tensile strength of 150,000 psi and Rockwell C33 hardness, this screw reliably handles extreme stress and vibration in heavy machinery and structural assemblies.
• Superior Corrosion Resistance – Zinc yellow-chromate plating provides a durable barrier against rust and environmental degradation, extending service life in harsh industrial settings.
• Optimized for High-Torque Applications – The external hex head and coarse UNC thread design ensure easy installation with standard tools and secure fastening under dynamic loads.
• Precision Thread Fit – Class 2A thread tolerance guarantees consistent engagement and reduces the risk of cross-threading, improving assembly efficiency and joint integrity.
• Versatile Partial Threading – The 2 1/4" minimum threaded section allows for effective clamping where unthreaded shank strength is needed, ideal for pivoting or shear-loaded connections.
• Compliance with Rigorous Standards – Meets ASME B18.2.1 specifications and environmental directives (RoHS 3, REACH), ensuring reliability and regulatory acceptance in global markets.
• Heavy-Duty Grade 8 Certification – Manufactured to Grade 8 standards, offering proven performance for critical applications in construction, mining, and transportation equipment.

Professional Applications & Engineering Value

Engineered for heavy-duty industrial applications, this Grade 8 hex head screw addresses common challenges in machinery assembly, structural steelwork, and heavy equipment manufacturing. The 7/8"-9 UNC coarse thread and partially threaded design provide excellent resistance to loosening under vibration, while the zinc yellow-chromate plating significantly enhances durability in corrosive environments such as outdoor construction or chemical processing plants. With 150,000 psi tensile strength and Rockwell C33 hardness, it ensures reliable performance in high-stress points, reducing maintenance frequency and downtime. The external hex drive allows for high-torque installation, making it a preferred choice for bolted connections requiring both strength and ease of assembly.

Specification Summary & Compliance

This screw adheres to Class 2A thread fit per UNC standards, ensuring precise dimensional accuracy. It conforms to ASME B18.2.1 and SAE J429 specifications for Grade 8 fasteners, with a length of 10 inches and partial threading starting from a minimum of 2 1/4 inches. The product is fully RoHS 3 (2015/863/EU) Compliant and REACH (EC 1907/2006) Compliant, meeting stringent environmental and safety regulations for industrial use worldwide.