S-91781A604 5/16"-18 x 5" ASME B18.6.3 Stainless Steel Slotted Flat Head Screws

Key Features & Benefits at a Glance

• Superior corrosion resistance with 18-8 Stainless Steel construction and passivated finish, ideal for harsh environments and extended service life.
• High tensile strength of 80,000 psi and Rockwell B80 hardness ensure reliable performance in demanding heavy-duty applications.
• Secure and precise fastening with Class 2A thread fit and UNC coarse threading, reducing the risk of cross-threading and assembly errors.
• Optimized for flush mounting thanks to the standard flat head profile and 82° countersink angle, providing a smooth surface finish.
• Easy manual installation and removal with the traditional slotted drive style, requiring only basic tools for maintenance.
• Partially threaded shank design allows for controlled clamping force and improved joint stability in various materials.
• Compliance with major industrial standards including ASME B18.6.3, ensuring dimensional accuracy and interchangeability.

Professional Applications & Engineering Value

This 5/16"-18 UNC flat head slotted screw is engineered to address critical fastening challenges in industrial settings. The 18-8 Stainless Steel material, combined with a passivated finish, provides exceptional resistance to corrosion, oxidation, and chemical exposure, making it suitable for outdoor, marine, and chemical processing equipment. The partially threaded design ensures that the unthreaded portion bears against the material, distributing load efficiently and preventing loosening under vibration—common in machinery, automotive assemblies, and structural frameworks. With a coarse thread spacing and Class 2A fit, these screws offer quick installation and reliable grip in wood, metal, and composite substrates, reducing assembly time and enhancing productivity. Ideal for applications requiring flush mounting, such as panels, fixtures, and enclosures, this screw delivers consistent performance where aesthetics and safety are paramount.

Specification Summary & Compliance

This product features precise Class 2A thread fit and adheres to UNC (Unified Coarse Thread) standards with a thread size of 5/16"-18. Manufacturing and dimensional specifications comply with ASME B18.6.3, ensuring uniformity and reliability. The screw is also compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, confirming it is free from hazardous substances and safe for use in various industrial and consumer applications.