distance core 26 is simultaneously moved along the threads 72 and 74 by motor 28 in a linear direction motor 28 may be programmed to change from one rate of speed to another during the linear and rotational movement of core 26 and from one rate of torque to another with corresponding changes to the linear and rotational responses in core 26 thus when it is desired to turn the core 26 with high torque and low speed or intermittently as when loosening and unscrewing the core from inside a hardened plastic article being molded such as fitting 20 the motor may be directed by a program to operate in that manner after the core has been loosened from the inside of the article and it is desired to move the core 26 out of and away from the plastic article more rapidly in a linear direction the motor 28 can be programmed to adopt a new speed and torque the change may be made if desired without interrupting the continuous rotation of the core in this assembly the movements of the core are very precisely controlled both linearly and rotationally so that core movements can be limited to specified thousandths of an inch.