S-91251A498 5/8"-18 x 1 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.
• Superior corrosion resistance with black-oxide coating protects against rust and extends service life in harsh industrial environments.
• Precision Class 3A thread fit provides tighter tolerances for secure, vibration-resistant assemblies in critical applications.
• Fine UNRF threads offer improved load distribution and better sealing capabilities compared to coarse threads.
• High hardness (Rockwell C37) enhances wear resistance and durability, maintaining thread integrity through repeated use.
• 1/2" hex drive design allows for high-torque installation with standard tools, ensuring efficient assembly and disassembly.
• Full threading along the 1-1/2" length provides consistent clamping force and flexibility in various mounting scenarios.

Professional Applications & Engineering Value

This black-oxide alloy steel socket head cap screw is engineered for demanding applications where high tensile strength and corrosion resistance are critical. The Class 3A UNRF fine thread ensures precise engagement in machinery, automotive, and aerospace assemblies, minimizing loosening from vibration. Its Rockwell C37 hardness and 170,000 psi tensile strength make it ideal for heavy-duty equipment, jigs, and fixtures subjected to dynamic loads. The black-oxide surface treatment provides added protection in humid or chemically aggressive environments, while the 1/2" hex drive facilitates secure installation in confined spaces. This fastener delivers reliable performance in industrial applications requiring strict dimensional accuracy and long-term durability.

Specification Summary & Compliance

This socket head cap screw features a 5/8"-18 UNRF fine thread with Class 3A fit for high-precision assemblies. It meets ASTM A574 specifications for alloy steel socket head cap screws and is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental standards. The product maintains strict dimensional accuracy, including a 1-1/2" length and fully threaded design, ensuring consistent performance in regulated industrial applications.