Firm-Coil® inserts are precision formed screw thread coils of stainless steel wire having a diamond shaped cross section. When they are installed into Firm-Coil® tapped holes, they provide permanent conventional 60' internal screw threads that accommodate any standard bolt or screw.

Free Running

In the free state they 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, nor interference fit is required to retain Firm-COIL Inserts, thereby eliminating stress concentration in the parent material. The  COIL Insert automatically adjusts itself, radially and axially, to any expansion or contraction of the parent material.