S-91251A834 4-40 x 2 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 high-stress conditions, reducing the risk of fastener failure in demanding applications.
• Superior corrosion resistance from the black-oxide finish on alloy steel, extending service life and maintaining integrity in harsh industrial environments.
• Precise Class 3A thread fit provides tighter tolerances for secure, vibration-resistant assemblies, minimizing loosening over time.
• Partially threaded design allows for controlled clamping force and easier alignment, ideal for components requiring specific grip ranges.
• High hardness (Rockwell C37) enhances wear resistance, ensuring the screw maintains its shape and drive compatibility through repeated use.
• Compatible with standard 3/32" hex drivers for quick installation and removal, streamlining maintenance and assembly processes.
• Compliance with ASTM A574, RoHS 3, and REACH guarantees material quality and environmental safety, meeting rigorous industry standards.

Professional Applications & Engineering Value

These black-oxide alloy steel socket head cap screws are engineered to address common industrial challenges, such as vibration-induced loosening and corrosion in machinery. The 4-40 UNC coarse threads with a Class 3A fit ensure precise engagement, reducing the need for frequent retightening in equipment like automotive assemblies, aerospace components, and heavy-duty manufacturing tools. The partially threaded configuration allows for optimal stress distribution, preventing damage to sensitive parts. With a 170,000 PSI tensile strength and Rockwell C37 hardness, they offer durability in high-load scenarios, while the black-oxide surface treatment provides an added layer of protection against rust, making them suitable for outdoor or humid environments. This combination of features supports efficient, long-term fastening solutions that minimize downtime and maintenance costs.

Specification Summary & Compliance

This socket head cap screw adheres to precise dimensional standards, including a Class 3A thread fit for tight tolerances and UNC coarse threads (4-40 size) with a minimum thread length of 3/4". It meets ASTM A574 specifications for alloy steel socket head cap screws, ensuring consistent manufacturing quality. Additionally, it is compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, confirming the absence of hazardous substances and supporting environmental safety in industrial applications.