main drive shaft 2 so that the shaft 30 is rotatable around and slidable along the center line of the shaft 30 a dial member 31 is secured to one end of the shaft 30 by a set screw 33 and is urged rightwardly as viewed in fig4 by a spring 32 the other end of the shaft 30 extends leftwardly in excess of a needle bar transfer plate 35 which is secured to the arm 1 by a screw 34 and a needle bar transfer arm 36 is secured to the end of the shaft 30 by a set screw 37 under the force of the spring 32 the arm 36 secured to the second mentioned end of the shaft 30 is ordinarily held in a sliding contact with the plate 35 while a gap l is ordinarily maintained between the rear side surface of the dial member 31 secured to the first mentioned end of the shaft 30 and the outer surface of the arm 1 through the transfer arm 36 pins 38 and 38 39 are extended toward the transfer plate 35 with the extended lengths adjusted by set screws 39 and 39 39 respectively on the other hand radially elongated holes 35a and 35a 39 are provided through the transfer plate for receiving either one of the pins 38 and 38 39 while arcuate escape holes 35b and 35b 39 are provided therethrough for receiving either one or both of the pins 38 and 38 39 in accordance with the rotation of the shaft 30 on the transfer plate 35 there are further provided.