S-99638A101 4-40 MS21045-04 Locknuts

Key Features & Benefits at a Glance

• Superior vibration resistance through flex-top locking design that maintains clamp load in high-stress environments
• Enhanced corrosion protection with cadmium yellow-chromate plating that withstands harsh industrial conditions
• Precise thread engagement with Class 3B fit ensuring reliable, consistent performance in critical assemblies
• Quick installation efficiency with standard external hex drive and coarse UNC threads for faster assembly times
• Military-grade reliability meeting MS21045-04 specifications for demanding aerospace and defense applications
• Optimized size compatibility with 1/4" width and 5/32" height fitting standard industrial components
• Durable steel construction providing long-term mechanical strength and fatigue resistance

Professional Applications & Engineering Value

This 4-40 UNC locknut delivers critical vibration-proof performance for aerospace assemblies, industrial machinery, and military equipment where safety cannot be compromised. The flex-top locking mechanism creates consistent friction against mating threads, eliminating the need for secondary locking devices and reducing assembly complexity. Manufactured from cadmium yellow-chromate plated steel, it provides exceptional corrosion resistance in challenging environments while maintaining the structural integrity required for high-vibration applications. The external hex drive enables secure tool engagement during installation, particularly valuable in confined spaces common in aircraft and precision equipment maintenance.

Specification Summary & Compliance

This locknut features 4-40 UNC coarse threads with Class 3B thread fit for precision engagement, right-hand thread direction, and complies with MS21045-04 military specifications. Dimensions include 1/4" width across flats and 5/32" height. The manufacturing process and materials meet relevant industry standards for high-performance locking fasteners in critical applications.