S-91251A109 2-56 x 1" 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.
• Superior wear resistance from Rockwell C37 hardness extends service life in demanding industrial environments.
• Precise Class 3A thread fit provides tighter tolerances for secure, vibration-resistant assemblies and improved load distribution.
• Corrosion-resistant black-oxide finish on alloy steel enhances durability and protects against rust in various operating conditions.
• Coarse UNC threads enable quicker installation and better performance in materials where fine threads may strip.
• Hex socket drive (5/64") allows for high-torque application with standard tools, minimizing cam-out and ensuring tight fastening.
• Compliance with ASTM A574, RoHS 3, and REACH guarantees material consistency, environmental safety, and suitability for regulated industries.

Professional Applications & Engineering Value

This Black-Oxide Alloy Steel Socket Head Cap Screw is engineered to address critical challenges in precision machinery, automotive assemblies, and heavy-duty equipment. The 2-56 UNC coarse thread design, combined with a Class 3A fit, ensures minimal backlash and superior resistance to loosening under dynamic loads. The partially threaded shank allows for controlled clamping force, reducing stress concentration in threaded sections. With a 170,000 psi tensile strength and Rockwell C37 hardness, it withstands extreme mechanical stresses and abrasive environments, making it ideal for applications requiring repeated disassembly. The black-oxide surface treatment not only adds corrosion protection but also reduces galling, facilitating smoother installation in high-volume production lines.

Specification Summary & Compliance

This screw adheres to UNC thread standards with a Class 3A thread fit for high precision. Dimensions include a 1" length, 5/64" hex drive, and 9/64" head diameter. It meets ASTM A574 specifications for alloy steel socket head cap screws, ensuring consistent material properties and manufacturing quality. The product is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, supporting use in environmentally conscious and global industrial supply chains.