S-91251A508 5/8"-18 x 5 1/2" ASTM A574 Alloy Steel Socket Head Screws

Key Features & Benefits at a Glance

• Superior corrosion resistance with black-oxide coating, ideal for harsh industrial environments
• Exceptional tensile strength of 170,000 psi ensures reliable performance under heavy loads
• Precision Class 3A thread fit provides secure fastening with minimal backlash in critical assemblies
• Rockwell C37 hardness maintains structural integrity and prevents thread deformation
• Fine UNF thread spacing offers superior vibration resistance compared to coarse threads
• Partially threaded design allows for precise clamping force control in specific applications
• 1/2" hex drive compatibility enables high-torque installation with standard tools

Professional Applications & Engineering Value

These black-oxide alloy steel socket head cap screws deliver critical performance advantages in demanding applications where precision and reliability are paramount. The 5/8"-18 UNF fine threads with Class 3A fit provide exceptional clamping force distribution, making them ideal for machinery, automotive assemblies, and precision equipment where vibration resistance is crucial. The partially threaded configuration allows engineers to precisely control engagement depth in critical joints, while the 170,000 psi tensile strength ensures structural integrity in high-stress applications. The combination of Rockwell C37 hardness and black-oxide surface treatment creates a durable fastener that withstands both mechanical stress and environmental exposure, solving common failure points in industrial fastening systems.

Specification Summary & Compliance

Manufactured to ASTM A574 specifications with Class 3A thread fit for precision applications. Features 5/8"-18 UNF fine threads with 0.625" diameter and 1 3/4" minimum thread length. Compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental standards. Right-hand thread direction with standard socket head profile and 1/2" hex drive compatibility.