1. First, heat the broken end (2 mm in length, to prepare the processing area) to dark red, and then slowly leave the flame (slowly cool down) to anneal and soften the clockwork material there.

2. Secondly, cut off the broken section, and file a new installation gap in the remaining annealed preparation area with a file.

3. Heat the previously heated area on the fire again until it is dark red, and then quickly leave the flame (rapid cooling) to harden the material.

4. Put the clockwork back and try to wind it up. Improper annealing and quenching treatment leads to poor material properties and re-fracture. Never mind, cut it off again and repeat the above operation, but slightly change the degree of heating.