S-91309A551 1/4"-20 x 2 1/4" ASME B18.2.1, ASTM A307 Low-Strength Steel Hex Head Screws

Key Features & Benefits at a Glance

• Exceptional tensile strength of 60,000 psi ensures reliable performance in demanding applications, reducing the risk of fastener failure.
• Superior corrosion resistance from zinc plating protects against rust and extends service life in harsh industrial environments.
• Coarse UNC threading provides faster installation and better performance in materials prone to stripping or cross-threading.
• Class 2A thread fit offers optimal clearance for easy assembly while maintaining secure fastening integrity.
• Full threading along the 2 1/4" length allows for maximum adjustability and grip in various material thicknesses.
• External hex drive design enables high-torque application with standard tools, speeding up installation and maintenance.
• Rockwell B69 hardness provides excellent durability and resistance to wear under repeated stress.

Professional Applications & Engineering Value

These 1/4"-20 UNC hex head screws are engineered to address critical fastening challenges in heavy-duty industrial applications. The steel construction with zinc plating combats corrosion in environments exposed to moisture and chemicals, significantly reducing maintenance frequency. The coarse thread design ensures secure engagement in soft materials and castings, preventing loosening from vibration—a common issue in machinery and structural assemblies. With full threading along the entire shank, these screws offer versatile clamping force distribution, making them ideal for construction, automotive, and manufacturing sectors where reliable, high-strength fastening is non-negotiable for operational safety and efficiency.

Specification Summary & Compliance

This product features a 1/4"-20 UNC coarse thread with Class 2A fit, ensuring standard dimensional accuracy and interchangeability. Manufactured in compliance with ASME B18.2.1 and ASTM A307 specifications, it meets rigorous engineering standards for mechanical properties. The screw is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, confirming its safety for use in regulated industries without hazardous substances.