S-91991A103 3/8"-16 Hex Nuts

Key Features & Benefits at a Glance

• Superior torque distribution with an extra wide profile that reduces stress concentration and prevents rounding during high-torque applications
• Enhanced corrosion resistance thanks to the black-oxide steel finish, extending service life in demanding industrial environments
• Reliable coarse thread engagement with UNC 3/8"-16 threading that resists vibration loosening and enables quick assembly
• Precise Class 2B thread fit ensuring consistent mating with Class 2A bolts for secure, play-free connections
• Optimized external hex drive design providing excellent tool access and reducing slippage during installation
• Compliance with global environmental standards including RoHS 3 and REACH, making it suitable for regulated industries
• Heavy-duty construction with 11/16" width and 23/64" height for increased load-bearing capacity in structural applications

Professional Applications & Engineering Value

This heavy-duty hex nut is engineered to address common industrial fastening challenges, including vibration-induced loosening and corrosion in harsh environments. The black-oxide steel construction provides superior protection against rust and oxidation, while the extra wide profile distributes clamping force more evenly across joined surfaces. The UNC coarse thread design ensures rapid installation and maintains integrity under dynamic loads, making it ideal for machinery, structural steel connections, and automotive assemblies where reliable fastening performance is critical. Its right-hand thread direction and external hex drive compatibility with standard tools streamline maintenance and replacement procedures in industrial settings.

Specification Summary & Compliance

This hex nut features Class 2B thread fit per UNC standards, ensuring dimensional accuracy and compatibility with Class 2A threaded components. Manufacturing adheres to inch system specifications with precise 3/8"-16 coarse threading. The product is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, meeting current environmental and safety requirements for industrial fasteners.