S-91257A559 1/4"-20 x 4 1/2" 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 Grade 8 strength rating and 150,000 psi tensile strength for reliable performance in high-stress industrial applications.
• Superior corrosion resistance provided by zinc yellow-chromate plating, extending service life in harsh environments and reducing maintenance costs.
• Optimized thread engagement with UNC coarse threading and Class 2A fit ensures quick assembly and vibration resistance in heavy machinery and structural applications.
• High torque capability through the external hex drive design and Rockwell C33 hardness, preventing stripping during installation in demanding conditions.
• Reduced inventory complexity with partial threading that combines the grip of unthreaded shank with threaded section versatility.
• Regulatory compliance assurance meeting ASME B18.2.1, SAE J429, RoHS 3, and REACH standards for global industrial projects.
• Dimensional precision with 4½" length and consistent 1/4"-20 thread size for reliable fit in inch-system applications.

Professional Applications & Engineering Value

These Grade 8 hex head screws deliver critical engineering solutions where failure is not an option. The 150,000 psi tensile strength and Rockwell C33 hardness provide exceptional resistance to shear and tensile forces in heavy equipment, construction frameworks, and industrial machinery. The zinc yellow-chromate plating creates a protective barrier against corrosion in outdoor or chemically aggressive environments, significantly extending maintenance intervals. The UNC coarse thread design ensures rapid assembly in thick materials while maintaining vibration resistance, and the partial threading offers optimal clamp load distribution. These heavy-duty fasteners are engineered to withstand extreme conditions while maintaining dimensional stability, making them ideal for structural connections, machinery assembly, and infrastructure projects requiring ASME B18.2.1 compliance.

Specification Summary & Compliance

Manufactured to precise dimensional standards with Class 2A thread fit tolerance for consistent performance. The 1/4"-20 UNC coarse thread follows standardized specifications with minimum thread length of ¾". These steel fasteners comply with ASME B18.2.1 and SAE J429 manufacturing standards, and meet environmental regulations including RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) compliance for hazardous substance restrictions.