an underwater pelletizer for cutting extruded plastic into a flow of liquid is disclosed . the pelletizer includes a cutter hub carrying at least one cutter blade , a cutter shaft for rotationally driving the cutter hub , and a flexible torque converter for connecting a motor to the cutter hub . in one embodiment , the torque converter has a first set of bushings that is fastened to a face of the cutter hub and a second set of bushings that is fastened to a face of the cutter shaft . the disclosed pelletizer has a shaft extension configured to engage a motor shaft , the shaft extension having an outer diameter having formed thereon a splined portion and first and second sealing surfaces . a disclosed motor adaptor has a seal surface . a water chamber plate may also have a seal surface . a first mechanical seal is illustratively configured to engage the first seal surface of the shaft extension and the seal surface of the motor adaptor . a second mechanical seal is illustratively configured to engage the second seal surface of the shaft extension and the seal surface of the water chamber plate . furthermore , a cutter shaft has a splined bore formed therein for engaging the splined portion of the shaft extension .