Special heat treatment is applied on the body, Hardness of striking part is slightly softer to prevent cracks, On the other hand cam part converts the striking power to twisted by striking with a hammer therefore this part is finished with higher hardness to improve anti-wear, Stronger spring is adapted to convert the striking power efficiently to twisting power Special heat treatment is applied on the body, Hardness of striking part is sl ightly softer to prevent cracks, On the other hand cam part converts the stri king power to twisted by striking with a hammer therefore this part is finish ed with higher hardness to improve anti-wear, Stronger spring is adapted to co nvert the striking power efficiently to twisting power,