S-91251A311 5/16"-18 x 5 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 in high-stress applications, reducing the risk of fastener failure.
• Superior corrosion resistance from the black-oxide coating extends service life in harsh industrial environments, minimizing maintenance needs.
• Precision Class 3A thread fit provides secure, vibration-resistant connections for improved assembly integrity.
• High hardness (Rockwell C37) offers excellent wear resistance, maintaining thread integrity through repeated use.
• Partially threaded design allows for precise clamping force control and easier alignment in assembled components.
• Standard hex drive compatibility with 1/4" drive enables quick installation and removal with common tools, boosting efficiency.
• Compliance with ASTM A574 and environmental regulations ensures consistent quality and safe use across various industries.

Professional Applications & Engineering Value

These black-oxide alloy steel socket head cap screws deliver critical engineering advantages in demanding applications such as heavy machinery, automotive assemblies, and industrial equipment. The UNC coarse thread design facilitates faster installation and provides superior resistance to vibration loosening compared to fine-thread alternatives. With 170,000 psi tensile strength and Rockwell C37 hardness, these fasteners maintain clamping force under extreme loads while the black-oxide surface treatment creates a protective barrier against rust and corrosion. The partially threaded configuration allows engineers to precisely control engagement length, preventing thread damage in blind holes and ensuring optimal stress distribution. These socket head cap screws solve common industrial challenges by combining high-strength performance with corrosion protection in a single, compliant fastener solution.

Specification Summary & Compliance

This 5/16"-18 UNC socket head cap screw features Class 3A thread fit for precision assembly, with a minimum thread length of 1-1/8" and overall length of 5-1/4". Manufactured to ASTM A574 specification for high-strength alloy steel socket head cap screws, these fasteners are RoHS 3 (2015/863/EU) Compliant and REACH (EC 1907/2006) Compliant, ensuring environmental responsibility and regulatory adherence for global industrial applications.