S-91251A400 5/8"-18 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 in high-stress applications, reducing the risk of fastener failure.
• Superior corrosion resistance from the black-oxide finish on alloy steel, extending service life in demanding industrial environments.
• Precise Class 3A thread fit provides tighter tolerances for secure, vibration-resistant assemblies in critical machinery.
• 1/2" hex drive design allows for high-torque installation with standard tools, speeding up assembly and maintenance processes.
• Fully threaded body offers consistent clamping force along the entire length, ideal for adjustable or deep-set applications.
• Compliance with ASTM A574 guarantees material consistency and manufacturing quality, ensuring repeatable performance.
• RoHS 3 and REACH compliance meets international environmental regulations, making it suitable for global supply chains.

Professional Applications & Engineering Value

This black-oxide alloy steel socket head cap screw is engineered to address common industrial challenges such as vibration loosening and corrosion in heavy machinery. The fine UNRF thread and Class 3A fit provide superior resistance to dynamic loads, making it ideal for precision equipment, automotive assemblies, and construction machinery where reliability is critical. The combination of high Rockwell C37 hardness and 170,000 psi tensile strength ensures that the fastener maintains integrity under extreme pressure, reducing maintenance downtime and enhancing operational safety. Its fully threaded design allows for versatile use in various clamping scenarios, offering engineers a dependable solution for high-stress, fine-thread applications.

Specification Summary & Compliance

This socket head cap screw features a 5/8"-18 UNRF fine thread with a Class 3A thread fit for precise engagement, and is manufactured from alloy steel with a black-oxide surface treatment. It complies with ASTM A574 specifications for material and manufacturing standards, and meets RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations, ensuring it is free from restricted substances for safe use in industrial and export markets.