S-91257A570 1/4"-28 x 3" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Hex Head Screws

Key Features & Benefits at a Glance

• Exceptional Strength for Demanding Loads: Grade 8 classification and 150,000 psi tensile strength ensure reliable performance in high-stress industrial applications.
• Superior Corrosion Resistance: Zinc yellow-chromate plating provides a durable barrier against rust and environmental degradation, extending the fastener's service life.
• Precise Thread Engagement: UNF fine thread with Class 2A fit offers excellent vibration resistance and secure fastening in critical assemblies.
• Optimized for High-Torque Applications: The external hex head design allows for easy installation and removal with standard tools, even in confined spaces.
• Enhanced Durability and Hardness: Rockwell C33 hardness rating ensures the screw maintains its integrity under repeated stress and wear.
• Versatile Partial Threading: The 3/4" minimum thread length provides a strong grip where needed while allowing for unthreaded shank flexibility in specific designs.
• Guaranteed Compliance and Quality: Manufactured to meet ASME B18.2.1 and SAE J429 standards, ensuring consistent dimensional accuracy and performance.

Professional Applications & Engineering Value

This Grade 8 hex head screw is engineered to address common challenges in heavy machinery, automotive, and construction sectors where joint failure is not an option. The steel construction, combined with the zinc yellow-chromate plating, provides a robust defense against corrosion, making it ideal for outdoor or harsh environment applications. The 1/4"-28 UNF fine thread ensures a tight, secure fit that resists loosening under vibration, a critical feature for dynamic load assemblies. Its partially threaded design allows the unthreaded shank to bear shear loads effectively, while the threaded portion delivers strong clamping force. By integrating high tensile strength and precise Class 2A thread fit, this fastener minimizes the risk of stripping and ensures long-term reliability in demanding industrial applications.

Specification Summary & Compliance

This screw adheres to strict dimensional and performance standards, including Class 2A thread fit for precise tolerance and UNF fine thread specifications. It is manufactured in compliance with ASME B18.2.1 and SAE J429 standards, ensuring consistent quality and interchangeability. The product is also fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, confirming its safety and environmental responsibility for global supply chains.