S-91251A104 3/8"-16 x 5 1/2" ASTM A574 Alloy Steel Socket Head Screws

Key Features & Benefits at a Glance

• Exceptional tensile strength of 170,000 psi ensures reliable performance under extreme loads and prevents fastener failure in demanding applications.
• Superior corrosion resistance from the black-oxide finish protects the alloy steel from rust and degradation, extending service life in harsh environments.
• Precise Class 3A thread fit guarantees secure, vibration-resistant assemblies with minimal risk of loosening, enhancing joint integrity.
• High hardness rating (Rockwell C37) provides excellent wear resistance and durability, maintaining fastener integrity through repeated use.
• Hex socket drive design allows for high torque application and easy installation in confined spaces, improving assembly efficiency.
• Compliance with ASTM A574 ensures consistent quality, material properties, and dimensional accuracy for reliable engineering use.
• RoHS 3 and REACH compliance makes these screws suitable for regulated industries and global supply chains, ensuring environmental and safety standards are met.

Professional Applications & Engineering Value

This Black-Oxide Alloy Steel Socket Head Cap Screw is engineered to solve critical challenges in heavy machinery, automotive, and industrial equipment assembly. The combination of 3/8"-16 UNC coarse threads and a Class 3A thread fit provides superior clamping force and vibration resistance, preventing joint failure in high-stress environments. The partially threaded design offers optimal grip and shear strength where full threading is not required. The black-oxide surface treatment significantly enhances corrosion resistance, making it ideal for applications exposed to moisture, chemicals, or outdoor conditions. Its 170,000 psi tensile strength and Rockwell C37 hardness ensure that it can withstand extreme mechanical loads without deforming, providing long-term reliability for critical connections in construction, manufacturing, and aerospace sectors.

Specification Summary & Compliance

This fastener features a 3/8"-16 UNC coarse thread with a precision Class 3A thread fit for tight tolerances and secure fastening. It is manufactured in accordance with ASTM A574 specifications, ensuring consistent material quality and mechanical properties. The product is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, confirming its suitability for use in environmentally conscious and regulated industrial markets.