S-91251A218 5-40 x 1 3/4" 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 from the black-oxide finish on alloy steel extends service life and maintains integrity in harsh industrial environments.
• Precise Class 3A thread fit provides tighter tolerances for secure, vibration-resistant assemblies, minimizing loosening over time.
• Hex socket drive design allows for easy installation with standard tools, offering better torque transmission and reduced risk of stripping compared to other drive types.
• Partially threaded shank enables optimal clamping force distribution, ideal for applications where precise grip length is critical.
• Compliance with ASTM A574, RoHS 3, and REACH ensures material consistency, environmental safety, and suitability for regulated industries.
• Coarse UNC threads facilitate quicker assembly and disassembly, improving efficiency in maintenance and production workflows.

Professional Applications & Engineering Value

These 5-40 UNC Socket Head Cap Screws are engineered to address common industrial challenges such as vibration-induced loosening and material fatigue. The black-oxide alloy steel construction, combined with a Rockwell C37 hardness, provides excellent durability and resistance to wear, making them ideal for heavy-duty machinery, automotive assemblies, and precision equipment. The partially threaded design ensures that the unthreaded portion bears against clamped materials, distributing load evenly and preventing joint failure. With a coarse thread profile, these screws offer faster installation in tough materials, reducing assembly time while maintaining Class 3A thread fit accuracy for leak-proof and secure connections in critical applications.

Specification Summary & Compliance

This product adheres to Class 3A thread fit tolerances for precise engagement, manufactured in accordance with ASTM A574 specifications for consistency and reliability. It meets RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) compliance standards, ensuring environmental safety and regulatory acceptance. The screws feature UNC coarse threads and are designed for right-hand threading applications, with dimensions including a 1-3/4" length and 3/32" hex drive size for standardized tool compatibility.