S-91274A178 1/4"-28 x 1/2" ASME B18.3, ASTM A574, ASTM B117 Alloy Steel Socket Head Screws

Key Features & Benefits at a Glance

• Exceptional tensile strength of 170,000 psi ensures reliable performance under high-stress conditions, reducing the risk of fastener failure.
• Superior corrosion resistance from zinc-flake coating extends service life in harsh or outdoor industrial environments.
• Precise Class 3A thread fit provides tighter tolerances for secure, vibration-resistant assemblies in critical applications.
• High hardness (Rockwell C37) offers excellent wear resistance, maintaining thread integrity through repeated use.
• Fully threaded design allows for consistent clamping force along the entire length, ideal for adjustable or deep-set applications.
• Standard hex drive (3/16") enables easy installation with common tools, reducing assembly time and improving efficiency.
• Compliance with major standards including ASME B18.3 and ASTM A574 guarantees consistent quality and interoperability.

Professional Applications & Engineering Value

This 1/4-28 UNF Socket Head Cap Screw is engineered for demanding industrial settings where precision and durability are non-negotiable. The zinc-flake-coated alloy steel construction provides robust protection against corrosion, making it suitable for automotive, aerospace, and heavy machinery applications exposed to moisture or chemicals. The fine thread spacing and Class 3A thread fit ensure minimal backlash and superior vibration resistance, critical in dynamic load environments. With a fully threaded right-hand design, it delivers uniform stress distribution, preventing loosening and maintaining clamp load integrity. These features collectively address common engineering challenges such as fastener fatigue, material degradation, and assembly inaccessibility, offering a reliable solution for high-performance bolting needs.

Specification Summary & Compliance

This socket head cap screw features a 1/4"-28 UNF fine thread with Class 3A fit for high precision. It meets ASME B18.3 for dimensional consistency and ASTM A574 for material quality. The zinc-flake coating is validated per ASTM B117 salt spray testing. The product is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, ensuring environmental safety and restricted substance adherence.