The MS21209 series defines self-locking wire thread inserts used in aerospace and defense applications to provide durable, vibration-resistant internal threads. These helical coil inserts are installed into tapped holes to repair damaged threads or reinforce threads in softer materials such as aluminum and magnesium.
MS21209 inserts incorporate a prevailing torque locking feature, typically achieved through controlled deformation of the insert coils, which helps prevent fasteners from loosening under vibration. This makes them well-suited for critical assemblies requiring secure and reusable fastening.
Manufactured from corrosion-resistant materials and available in a range of thread sizes and lengths, MS21209 inserts are widely used across aircraft structures, engines, and mechanical systems. Many have been superseded by NASM21209, the current aerospace standard.
