S-91257A107 1/4"-20 x 5 1/4" 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 in high-stress applications, reducing the risk of fastener failure.
• Superior corrosion resistance with zinc yellow-chromate plating extends service life in harsh industrial or outdoor environments.
• High hardness rating (Rockwell C33) provides excellent wear resistance and maintains thread integrity under repeated use.
• Coarse UNC threading allows for faster installation and better performance in materials where fine threads might strip or fail.
• Partially threaded design offers optimal clamping force for joints requiring precise unthreaded shank sections.
• External hex drive enables high-torque installation with standard tools, ensuring secure fastening in heavy-duty assemblies.
• Grade 8 certification guarantees consistent quality and compliance with rigorous industrial standards for demanding applications.

Professional Applications & Engineering Value

Engineered for heavy-duty industrial applications, these Grade 8 hex head screws deliver critical reliability where failure is not an option. The steel construction combined with 150,000 PSI tensile strength addresses common challenges in machinery assembly, structural framing, and equipment manufacturing where vibration and dynamic loads can compromise inferior fasteners. The zinc yellow-chromate plating provides essential corrosion protection in environments exposed to moisture, chemicals, or outdoor elements, significantly extending maintenance intervals. With UNC coarse threading and partial threading, these screws offer superior grip in both soft and hard materials while preventing joint loosening. Their 5 1/4" length and external hex drive make them ideal for applications requiring deep penetration and high torque installation, from construction equipment to industrial machinery frames.

Specification Summary & Compliance

These hex head screws feature precise Class 2A thread fit tolerances ensuring consistent engagement and proper clearance. Manufacturing complies with ASME B18.2.1 and SAE J429 Grade 8 specifications, guaranteeing dimensional accuracy and mechanical properties. The 1/4"-20 UNC coarse thread configuration provides reliable performance in various materials, while the zinc yellow-chromate plating meets industry standards for corrosion protection. All materials and processes conform to RoHS and REACH environmental directives.