S-91257A748 1/2"-20 x 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 a tensile strength of 150,000 psi, this screw reliably handles extreme mechanical stresses in demanding industrial environments.
• Superior Corrosion Resistance: The zinc yellow-chromate plating provides a durable barrier against rust and corrosion, extending the fastener's service life.
• High-Strength Material Grade: Manufactured from Grade 8 steel with a Rockwell C33 hardness, ensuring high durability and resistance to shear and vibration.
• Precise Thread Engagement: The Class 2A thread fit and UNF fine thread spacing offer excellent vibration resistance and secure fastening in critical assemblies.
• Optimized for High-Torque Applications: The external hex drive and 3/4" head width allow for easy installation with standard tools, even under high torque requirements.
• Versatile Partially Threaded Design: Combines a strong, unthreaded shank with a threaded portion, ideal for applications requiring clamping force and precise alignment.
• Compliance with Major Standards: Meets ASME B18.2.1 and SAE J429 specifications, ensuring consistent quality and interchangeability.

Professional Applications & Engineering Value

This Grade 8 hex head screw is engineered to solve critical fastening challenges in heavy machinery, construction equipment, and automotive assemblies where failure is not an option. Its 1/2"-20 UNF fine thread and partially threaded design provide superior resistance to loosening under dynamic loads and vibrations, a common pain point in industrial settings. The zinc yellow-chromate plating offers robust protection against harsh environmental conditions, including exposure to moisture and chemicals, significantly reducing maintenance needs and downtime. By specifying this high-strength bolt, engineers and procurement professionals can ensure reliable performance in structural connections, engine components, and other industrial applications that demand uncompromising safety and durability.

Specification Summary & Compliance

This fastener adheres to precise dimensional standards, including a Class 2A thread fit and UNF thread type with fine spacing, manufactured in accordance with ASME B18.2.1 and SAE J429. It is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, ensuring it is free from hazardous substances and suitable for use in regulated markets.