and inserted through the spring member 53 into the accommodation hole 521 the cutter blades 26 are affixed to one end of the locating member 55 outside the cutter holder 52 and rotatable and axially movable with the locating member 55 the plug member 56 is mounted in the accommodation hole 521 of the cutter holder 52 around the locating member 55 and connected to the coupling shaft 51 for enabling the locating member 55 to be rotated with the coupling shaft 51 referring to fig1 7 during operation of the plastic pelletizing machine the motor 11 of the rotary drive 1 is controlled to rotate the driving shaft 12 thereby rotating the transmission shaft 21 of the transmission unit 2 and the coupling shaft 51 of the cutter unit 5 when going to move the cutter blade 54 of the cutter unit 5 into contact with the plastic pelletizing machine 39 s perforated plate 6 the inductor 42 of the linear motor 4 is activated to move in direction away from the motor body 41 of the linear motor 4 thereby carrying the bearing block 22 in direction toward the perforated plate 6 when the bearing block 22 is moved in direction toward the perforated plate 6 the transmission shaft 21 is carried by the bearing block 22 to move the cutter unit 5 toward the perforated plate 6 forcing the cutter blade 54 into contact with the plastic pelletizing machine 39 s perforated plate 6 further during.