S-99638A300 5/16"-24 MS21045-5 Locknuts

Key Features & Benefits at a Glance

• Superior vibration resistance through flex-top locking design that maintains clamp force under extreme conditions
• Enhanced corrosion protection with cadmium yellow-chromate plating for extended service life in harsh environments
• Precision thread engagement with Class 3B fit ensuring reliable, consistent fastening performance
• Aerospace-grade certification meeting MS21045-5 standards for critical applications requiring verified quality
• Optimal torque transmission via standard external hex design compatible with common industrial tools
• Fine thread configuration (24 TPI) providing superior resistance to loosening compared to coarse threads
• Right-hand threading compatibility with standard UNF fastening systems for seamless integration

Professional Applications & Engineering Value

This 5/16"-24 UNF flex-top locknut delivers critical vibration resistance in demanding aerospace, automotive, and industrial machinery applications where fastener failure is not an option. The cadmium yellow-chromate plated steel construction provides dual protection against corrosion and galvanic reactions, while the flex-top locking mechanism creates consistent spring tension that compensates for thermal expansion and vibration-induced loosening. Engineered with Class 3B thread fit, this locknut maintains precise tolerances for high-stress assemblies where fine thread engagement is essential for load distribution. The MS21045-5 certification validates its performance in critical aerospace applications, making it the trusted choice for engineers specifying components for vibration-prone environments.

Specification Summary & Compliance

This locknut features 5/16"-24 UNF fine threads with Class 3B thread fit for precision engagement, manufactured to MS21045-5 military specifications. The external hex drive measures 1/2" across flats with a 23/64" height profile. The cadmium yellow-chromate plating on steel substrate provides corrosion resistance while maintaining compliance with aerospace and industrial standards. Components meet relevant industry specifications for high-performance locking fasteners in critical applications.