which the motor is stopped subsequently in step 708 it is checked whether the m th needle is still in position if yes the m th needle is in position as the current working needle and the procedure goes to step 709 and ends there if not it is indicated that the sewing head is overshot and the m th needle is not in position above the circular opening in this case the procedure goes to step 710 in which the motor is driven to rotate in the negative direction and whereby the spiral shaft is caused to move to the right subsequently in step 711 it is detected whether or not the m th needle is in position if not the procedure returns to step 710 in which the motor is kept moving in the negative direction until the m th needle is in position when the m th needle is in position the procedure goes to step 712 in which the motor is stopped next in step 713 it is detected whether or not the m th needle is still in position if yes it is assured that the m th needle is in position as the working needle the procedure thus goes to step 709 and ends there if not it is indicated that the sewing head is overshot and the procedure returns to step 705 in which the motor is driven to rotate reversely.