Heli-Coil free-running and screw-locking Inserts are the original—and have an extensive background of tension, torque, shear, vibration, and fatigue tests conducted by the industry's leading companies as well as the U.S. Military.
Successful applications in the fields of aviation, electronics, industrial, automotive, and military equipment provide a wealth of experience and confidence in the performance and reliability of Heli-Coil inserts.
Free-running and screw-locking inserts available in metric coarse, metric fine, UNC, and UNF varieties.
In the free state, free-running inserts are greater in diameter than the tapped hole into which they are installed. In the assembly operation, the torque applied to the tang reduces the diameter of the leading coil and permits it to enter the tapped thread. When the torque or rotation is stopped, the coils expand with a spring-like action, anchoring the insert permanently in place against the tapped hole. No staking, locking, swaging, keying, or interference fit is required to retain free-running inserts, thereby eliminating stress concentration in the parent material. Free-running inserts automatically adjust themselves, radially and axially, to any expansion or contraction of the parent material.
Screw-locking inserts provide an exclusive, resilient internal locking thread that grips the bolt and prevents it from loosening under vibration or impact.
Locking action is achieved by one or more of the coils of the insert having a series of straight segments, or chords. When the bolt enters this grip coil, these chordal segments flex outward creating pressure on the bolt. This pressure is exerted between the flanks of the bolt thread thus utilizing the maximum contact area and minimizing the unit pressure.
Screw-lock inserts permit repeated assembly and disassembly yet will not relax their grip on the screw even in tough metals such as cast iron, alloy steel, titanium, etc.
Features and benefits: