S-91251A659 5/16"-18 x 6 1/4" 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 coating extends service life in harsh industrial environments, minimizing maintenance needs.
• Precise Class 3A thread fit provides tighter tolerances for secure, vibration-resistant assemblies in critical machinery.
• High hardness (Rockwell C37) offers excellent wear resistance, maintaining thread integrity through repeated use.
• Hex socket drive design allows for high torque application and easy installation in confined spaces with standard tools.
• Partially threaded shank enables optimal clamping force distribution, ideal for components requiring precise alignment.
• Compliance with ASTM A574, RoHS 3, and REACH ensures material consistency and environmental safety for global supply chains.

Professional Applications & Engineering Value

Engineered for demanding industrial settings, these black-oxide alloy steel socket head cap screws address common fastening challenges like vibration loosening and corrosion-induced degradation. The UNC coarse thread design facilitates quicker assembly in soft materials or where debris accumulation is a concern, while the 1/4" hex drive accommodates high-torque tools without stripping. With a 170,000 PSI tensile strength and Rockwell C37 hardness, they provide durable solutions for heavy machinery, automotive assemblies, and construction equipment, ensuring long-term reliability under dynamic loads. The partial threading allows unthreaded sections to act as precision guides, reducing shear stress in bolted joints.

Specification Summary & Compliance

This screw adheres to Class 3A thread fit for precise dimensional accuracy and meets ASTM A574 specifications for alloy steel socket head cap screws. It is manufactured with 5/16"-18 UNC coarse threads and a right-hand thread direction, ensuring compatibility with standard components. Regulatory compliance includes RoHS 3 (2015/863/EU) and REACH (EC 1907/2006), confirming the absence of restricted hazardous substances for safe industrial use.