heli coil
A Helicoil is a metallic threaded insert for repairing and reinforcing damaged internal threads. It is made from Austenitic stainless steel wire such as AISI 302/304 or Inconel X-750 alloy with a square or diamond cross-section. The wire diameter typically ranges from 0.6 to 2 mm, graded according to ISO 9001:2015. Helicoils are available in metric M2 to M48 and unified UNC/UNF thread sizes. The ultimate tensile strength of standard steel inserts is at least 1400 MPa. Installation requires creating a starter thread using a special drill and tap steyer. After installation, the inserts back-out torque is up to 40% higher than the original threads. This feature secures the connection against vibration-induced loosening.
The Helicoil structure is a spring-like coil with a 90-degree wind angle and a short lead-in tang. Surface coatings like silver or PTFE are sometimes used to reduce friction and improve electrical properties. According to aerospace standards like NASM 33575 or MS 21209, it must withstand temperature cycles from -55°C to +260°C. Quality control tests include torsional tension, sealing tests, and salt spray corrosion resistance checks. Its primary applications are in aircraft engines, braking systems, and aluminum cylinder blocks. The inserts are permanently locke
