S-91251A559 1/4"-20 x 4 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 in demanding applications.
• Superior corrosion resistance provided by the black-oxide finish on alloy steel, extending service life and maintaining integrity in harsh industrial environments.
• Precise Class 3A thread fit guarantees secure, vibration-resistant connections, minimizing loosening and enhancing assembly stability.
• Partially threaded design allows for controlled clamping force and easier alignment, streamlining installation in complex machinery and equipment.
• High hardness (Rockwell C37) offers excellent wear resistance, maintaining thread integrity and drive features through repeated use and high torque applications.
• Hex socket drive (3/16") enables high torque application with standard tools, facilitating quick and secure fastening in confined spaces.
• Compliance with ASTM A574, RoHS 3, and REACH ensures material quality, environmental safety, and global regulatory acceptance for worry-free procurement.

Professional Applications & Engineering Value

This Black-Oxide Alloy Steel Socket Head Cap Screw is engineered to address critical challenges in heavy-duty industrial assemblies, such as machinery, automotive systems, and construction equipment. The coarse UNRC thread and Class 3A fit provide superior resistance to vibration and dynamic loads, preventing joint failure in high-stress environments. With a partially threaded shank, it allows precise load distribution and reduces stress concentration, ideal for applications requiring exact clamping force. The black-oxide surface treatment enhances corrosion resistance, ensuring longevity in humid or corrosive conditions without compromising the 170,000 psi tensile strength. By integrating these features, this fastener delivers reliable performance, reduces maintenance downtime, and supports efficient assembly processes in sectors demanding durability and precision.

Specification Summary & Compliance

This socket head cap screw adheres to inch system dimensions with a thread size of 1/4"-20 and Class 3A thread fit for precise tolerance. It conforms to ASTM A574 specifications for high-strength alloy steel fasteners, ensuring consistent quality and performance. The product is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, confirming it is free from hazardous substances and safe for industrial use worldwide.