S-91355A084 5/16"-18 x 3/8" ASME B18.3, ASTM F835 Steel Flanged Button Head Hex-Drive Screws

Key Features & Benefits at a Glance

• Exceptional Durability: Crafted from Black-Oxide Alloy Steel with a Rockwell C39 hardness to resist wear and deformation in demanding industrial environments.
• Superior Fastening Strength: Delivers a high 120,000 psi tensile strength, ensuring reliable, vibration-resistant connections for heavy-duty applications.
• Precise & Secure Thread Fit: Features a Class 3A UNC coarse thread for easier, faster assembly and a tighter, more secure fit compared to standard classes.
• Enhanced Torque Application: The hex drive (3/16") allows for high-torque installation with common tools, reducing the risk of stripping and improving installation efficiency.
• Integrated Flange Design: The built-in flange (0.688" diameter) distributes clamping force over a wider area, eliminating the need for a separate washer and providing a more stable joint.
• Full Thread Engagement: Fully threaded design maximizes grip length and pull-out resistance for a stronger hold in various materials.
• Corrosion-Resistant Finish: The black-oxide coating provides a protective layer against rust and oxidation, extending the screw's service life.

Professional Applications & Engineering Value

This 5/16"-18 x 3/8" rounded head screw is engineered to solve critical fastening challenges in industrial and heavy machinery applications. The combination of high-strength alloy steel and a Class 3A UNC coarse thread ensures rapid assembly and a vibration-resistant fit, preventing loosening under dynamic loads. The flanged, rounded button head provides a low-profile, finished appearance while the integrated flange acts as a built-in washer, saving assembly time and reducing component count. Its black-oxide finish offers reliable protection in moderately corrosive environments, making it an ideal, durable solution for construction equipment, automotive assemblies, and robust metal frameworks where reliability and high tensile strength are non-negotiable.

Specification Summary & Compliance

This screw features a 5/16"-18 UNC thread with coarse spacing and a precision Class 3A thread fit for superior dimensional accuracy. It is manufactured in compliance with the ASME B18.3 specification where identified by ASTM F835. The product is also verified to be RoHS 3 (2015/863/EU) Compliant and REACH (EC 1907/2006) Compliant, ensuring it meets stringent environmental and safety regulations for industrial use.