S-90403A843 5/16"-18 x 1/2" ASME B18.13 Steel Pan Head Phillips Screws with Internal-Tooth Lock Washer

Key Features & Benefits at a Glance

• Superior vibration resistance with integrated internal-tooth lock washer that maintains clamping force under dynamic loads
• Enhanced corrosion protection through zinc-plated steel construction for extended service life in demanding environments
• Optimized drive engagement with Phillips No. 4 drive for efficient installation and reduced cam-out risk
• Maximum thread engagement through fully threaded design ensuring superior holding power across the entire fastener length
• Precise fit and compatibility with Class 2A thread tolerance for reliable assembly in UNC coarse thread applications
• High mechanical strength delivering 60,000 psi tensile strength and Rockwell B69 hardness for heavy-duty applications
• Standard-compliant reliability meeting ASME B18.13 specifications for consistent performance and interchangeability

Professional Applications & Engineering Value

Engineered for demanding industrial environments, these zinc-plated steel rounded head screws combine mechanical strength with vibration-resistant locking technology to solve critical fastening challenges. The internal-tooth lock washer creates permanent resistance against loosening in high-vibration machinery, automotive assemblies, and heavy equipment. With UNC coarse threads and Class 2A fit, these fasteners provide rapid installation and reliable performance in structural applications where tensile strength and thread integrity are paramount. The zinc-plated surface treatment offers essential corrosion protection for industrial settings, while the pan head profile with Phillips drive ensures flush mounting and efficient torque transfer during assembly operations.

Specification Summary & Compliance

This fastener features precision 5/16"-18 UNC coarse threads with Class 2A thread fit for consistent dimensional accuracy. Manufactured to meet ASME B18.13 specifications for mechanical fasteners, ensuring reliable performance and interchangeability. Compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations, confirming the absence of restricted hazardous substances. The zinc-plated steel construction provides both corrosion resistance and mechanical properties suitable for industrial applications requiring 60,000 psi tensile strength and Rockwell B69 hardness.