S-91257A112 1/4"-28 x 1 3/8" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Hex Head Screws

Key Features & Benefits at a Glance

• Maximum load-bearing capacity with 150,000 psi tensile strength and Rockwell C33 hardness for demanding applications
• Superior corrosion resistance through zinc yellow-chromate plating that protects against harsh industrial environments
• Precise thread engagement with Class 2A thread fit ensuring reliable fastening and vibration resistance
• Optimized torque transmission through external hex drive design that prevents tool slippage during installation
• Enhanced fatigue resistance with UNF fine threading that distributes stress more evenly across threads
• Versatile partial threading allowing unthreaded shank sections to function as precision alignment pins
• Industry-standard compliance meeting ASME B18.2.1 and SAE J429 specifications for guaranteed interchangeability

Professional Applications & Engineering Value

These Grade 8 hex head screws deliver exceptional engineering value in heavy machinery, automotive assemblies, and structural frameworks where vibration resistance and long-term reliability are critical. The combination of 150,000 psi tensile strength and Rockwell C33 hardness ensures these fasteners maintain clamp force under extreme dynamic loads, while the zinc yellow-chromate plating provides superior protection against corrosion in outdoor or chemically aggressive environments. The 1/4"-28 UNF fine threading offers increased thread engagement compared to coarse threads, making these partially threaded screws ideal for applications requiring precise alignment through the unthreaded shank section. Engineered to ASME B18.2.1 and SAE J429 standards, these industrial fasteners guarantee dimensional consistency and reliable performance across manufacturing and maintenance operations.

Specification Summary & Compliance

This Grade 8 hex head screw features precise Class 2A thread fit tolerances with 1/4"-28 UNF fine threading in right-hand direction. The fastener measures 1 3/8" in length with 3/4" minimum thread length and 7/16" hex head width for standard tool compatibility. Manufactured to meet ASME B18.2.1 dimensional specifications and SAE J429 material and mechanical property requirements, ensuring full compliance with industrial quality standards for heavy-duty applications.