S-91257A756 1/2"-20 x 6" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Hex Head Screws

Key Features & Benefits at a Glance

• Exceptional tensile strength of 150,000 psi ensures reliable performance under extreme loads, reducing the risk of fastener failure in critical applications.
• Superior corrosion resistance from zinc yellow-chromate plating extends service life in harsh industrial environments, minimizing maintenance and replacement costs.
• High hardness rating (Rockwell C33) provides excellent wear resistance and durability, maintaining thread integrity through repeated use.
• Precision Class 2A thread fit with UNF fine threading offers secure, vibration-resistant connections and easier assembly in high-stress applications.
• External hex drive design allows for high-torque installation with standard tools, speeding up assembly and disassembly processes.
• Partial threading provides an unthreaded shank for enhanced shear strength and precise clamping in structural connections.
• Full compliance with ASME B18.2.1/SAE J429 standards guarantees consistent quality, dimensional accuracy, and interoperability in regulated industrial settings.

Professional Applications & Engineering Value

This Grade 8 hex head screw is engineered to address common industrial fastening challenges where vibration, heavy loads, and environmental exposure compromise joint integrity. The 1/2"-20 UNF fine thread configuration delivers superior clamping force and resistance to loosening in dynamic applications such as heavy machinery, construction equipment, and automotive assemblies. Manufactured from high-strength steel and finished with zinc yellow-chromate plating, it combats corrosion in outdoor or chemically aggressive settings. The partially threaded design concentrates stress away from the threaded portion, enhancing fatigue resistance in structural connections. Ideal for OEM and MRO applications requiring high tensile strength and long-term reliability, this fastener ensures consistent performance in demanding industrial hex screw installations.

Specification Summary & Compliance

This fastener maintains precise Class 2A thread fit tolerances per UNF standards, with a 1/2"-20 thread size and 6" length. It fully complies with ASME B18.2.1 dimensional specifications and SAE J429 material and mechanical property requirements for Grade 8 fasteners. Manufacturing adheres to industry standards for inch fasteners, ensuring dimensional consistency and mechanical performance. The zinc yellow-chromate plating meets common corrosion protection specifications for industrial use, supporting compliance with RoHS and REACH environmental directives where applicable.