S-91251A458 1/4"-28 x 3 1/4" ASTM A574 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 the black-oxide finish extends service life in demanding industrial environments.
• Precise Class 3A thread fit provides tighter tolerances for secure, vibration-resistant assemblies in critical applications.
• Fine UNF threads offer improved load distribution and better adjustment accuracy compared to coarse threads.
• Partially threaded design allows for controlled clamping force and easier alignment in assembled components.
• Hex socket drive enables high torque application with reduced risk of cam-out, ensuring efficient installation.
• Compliance with ASTM A574, RoHS 3, and REACH guarantees material consistency and environmental safety for global supply chains.

Professional Applications & Engineering Value

Engineered for precision and durability, this black-oxide alloy steel socket head cap screw addresses common industrial challenges such as vibration loosening and corrosion. The Class 3A UNF fine thread ensures minimal backlash and enhanced sealing in high-precision machinery, automotive, and aerospace assemblies. Its 170,000 PSI tensile strength and Rockwell C37 hardness provide reliable performance in heavy-load applications, while the partially threaded shank allows for optimal stress distribution. The black-oxide surface treatment not only resists rust but also reduces galling, making it ideal for repeated disassembly in maintenance-critical environments. These screws are trusted in industrial fastening systems where strength, compliance, and longevity are non-negotiable.

Specification Summary & Compliance

This socket head cap screw meets ASTM A574 specifications for high-strength metric and inch-series fasteners. It features a Class 3A thread fit for precise engagement and a 1/4"-28 UNF fine thread with right-hand direction. The product is fully RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) compliant, ensuring adherence to environmental and safety regulations. Dimensions include a 3 1/4" length with a minimum thread length of 1", a 3/8" head diameter, and a 3/16" hex drive for standard tool compatibility.