S-90128A321 5/16"-18 x 1 5/8" ASME B18.3, 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 in demanding applications.
• Superior corrosion resistance provided by the zinc plating on alloy steel, extending service life and maintaining integrity in harsh industrial environments.
• Precision Class 3A thread fit guarantees tight, secure fastening with minimal play, ideal for applications requiring exact alignment and vibration resistance.
• High hardness rating (Rockwell C37) enhances wear resistance and durability, ensuring the screw maintains its form and function over repeated use.
• Standard hex drive design with a 1/4" drive size allows for easy installation and removal using common tools, improving assembly efficiency.
• Coarse UNC threads enable quicker installation and better grip in a variety of materials, reducing assembly time and enhancing holding power.
• Compliance with major standards including ASME B18.3 and ASTM A574, ensuring quality, consistency, and reliability for professional engineering use.

Professional Applications & Engineering Value

These zinc-plated alloy steel socket head cap screws are engineered to address common industrial challenges such as vibration loosening, corrosion, and high mechanical stress. The Class 3A thread fit and coarse UNC thread form provide superior clamping force and resistance to dynamic loads, making them ideal for machinery, automotive assemblies, and heavy equipment where precision and reliability are critical. The partially threaded design allows for controlled engagement, minimizing thread damage and ensuring secure fastening in tapped holes or with nuts. Combined with a 1/4" hex drive, they facilitate efficient maintenance and reduce downtime in production environments, while the zinc plating offers added protection against rust in outdoor or humid conditions, supporting long-term operational safety and cost-effectiveness.

Specification Summary & Compliance

This product adheres to precise dimensional standards, including a Class 3A thread fit for tight tolerances and UNC coarse threads with a size of 5/16"-18. It meets ASME B18.3 and ASTM A574 specifications for material and manufacturing quality. Additionally, it is compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, ensuring environmental safety and restricted substance-free composition for global industrial use.