S-91251A210 4-40 x 1 3/8" 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.
• Corrosion-resistant black-oxide finish on alloy steel provides enhanced durability and protection against rust, extending service life in harsh industrial environments.
• Precise Class 3A thread fit offers superior engagement and vibration resistance, minimizing loosening and ensuring secure, long-lasting assemblies.
• Hex socket drive design allows for high torque application and easy installation in confined spaces, improving assembly efficiency and reducing labor time.
• Partially threaded shank with a minimum 3/4" thread length provides optimal grip and clamping force, ideal for components requiring precise positioning.
• Compliance with ASTM A574, RoHS 3, and REACH standards guarantees material consistency, environmental safety, and suitability for regulated industries.
• Coarse UNC threads enable quick assembly and disassembly, reducing installation time and maintenance costs in high-volume production settings.

Professional Applications & Engineering Value

Engineered for precision and resilience, this 4-40 UNC Socket Head Cap Screw is crafted from black-oxide alloy steel to address common industrial challenges such as corrosion, vibration loosening, and high mechanical stress. The Rockwell C37 hardness and robust 170,000 psi tensile strength make it ideal for heavy-duty applications in machinery, automotive assemblies, and aerospace components, where failure is not an option. The hex drive and standard socket head profile facilitate secure tightening in tight spaces, while the coarse thread design ensures rapid installation. By meeting ASTM A574 specifications, it delivers consistent performance in critical fastening tasks, reducing downtime and maintenance costs for engineering teams.

Specification Summary & Compliance

This screw adheres to Class 3A thread fit for precise dimensional accuracy and superior thread engagement. Manufactured in accordance with ASTM A574, it ensures high-quality alloy steel construction. The product is fully RoHS 3 (2015/863/EU) Compliant and REACH (EC 1907/2006) Compliant, confirming its safety for use in regulated environments without hazardous substances.