BaerCoil® Instructions for use for thread repair

1. Core drilling

Core hole drilling in cross section

Drill out damaged thread with twist drill.
Drilling is not necessary for spark plug threads; use the combined drilling and cutting tool here.
Optionally, the hole can be countersunk with a taper countersink.

2. Thread cutting

Thread cutting in cross section

Use special Baercoil tap to cut the holding thread in the hole. BaerCoil taps are suitable for blind hole and through hole. The use of cutting oil is recommended.

3. Install thread insert

Install thread insert in cross section

Place the thread insert on the tool. Then fix the set collar so that the tang of the threaded insert sits in the center of the groove. Then, under light pressure, screw the threaded insert into the receiving thread until it is seated 1/4 - 1/2 turns below the surface.
DO NOT turn against the direction of travel, as the tang may break off.

4. Tang break

Tenon crushing in cross section

Retract the installation tool and rotate it 90° so that it is seated on the trunnion. Briefly tap the rear of the tool. If present, remove the trunnion with a trunnion breaker. For larger dimensions and for spark plug threads, remove the trunnion with needle-nose pliers.

Possible length adjustment

Shortening a wire thread insert with side cutter

BaerCoil thread inserts can be shortened, according to the required length, with a side cutter or similar.

When these operations are completed, the tight and exact tolerances, as well as the forming of the spring thread, have resulted in a thread that is often better and stronger than the original thread.


  • Thread forming of materials with low shear strength, e.g. aluminum and plastic, in mechanical engineering, automotive, electrical, medical and aerospace industries
  • Thread repair of damaged and worn threads.
  • Scrap recovery

Application video: Thread repair with BaerCoil®