S-91251A890 7/8"-9 x 4 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, reducing the risk of fastener failure in critical assemblies.
• Superior corrosion resistance from the black-oxide finish prolongs service life in harsh industrial environments, minimizing maintenance and replacement costs.
• Precise Class 3A thread fit provides consistent engagement and vibration resistance, enhancing joint integrity and assembly reliability.
• High hardness (Rockwell C37) offers excellent wear resistance, maintaining thread form and drive integrity through repeated use.
• Coarse UNRC threads enable faster installation and reduced cross-threading risks, improving assembly efficiency in production lines.
• Partially threaded design allows for controlled clamping force distribution, ideal for applications requiring precise unthreaded shank sections.
• 3/4" hex drive compatibility ensures secure tool engagement and high torque transmission, preventing stripping during installation.

Professional Applications & Engineering Value

Engineered for demanding industrial applications, these black-oxide alloy steel socket head cap screws deliver exceptional performance where high tensile strength and corrosion resistance are critical. The UNRC coarse thread configuration combined with Class 3A thread fit ensures reliable fastening in heavy machinery, construction equipment, and automotive assemblies where vibration resistance is paramount. The partially threaded design provides optimal stress distribution when securing thick materials or components requiring precise clamping zones. With 170,000 psi tensile strength and Rockwell C37 hardness, these screws maintain structural integrity under dynamic loads and extreme conditions, making them ideal for critical connections in manufacturing, aerospace, and heavy equipment industries where fastener failure is not an option.

Specification Summary & Compliance

These socket head cap screws feature 7/8"-9 UNRC coarse threads with Class 3A thread fit for precision engagement and 4 1/2" length with 2 1/4" minimum thread length. Manufactured to ASTM A574 specifications for high-strength alloy steel fasteners, they comply with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations, ensuring safe use in regulated industries worldwide.