Abstract: A cutting tool system is provided that includes a locking collar and a bit attachment member. The locking collar is compressible radially inwardly and has a tapering outer surface. The bit attachment member has a tapering inner surface constructed to receive and interface with the outer surface of the locking collar. According to an embodiment, a first groove in the outer surface of the locking collar is alignable with a second groove of the bit attachment member to form a perimeter of a pin receptacle in which is pin is insertable to prevent relative rotation between the locking collar and the bit attachment member. According to another embodiment, the cutting tool system further includes a retainer plate and fasteners constructed to secure the retainer plate directly to the locking collar and to the driving shaft, and to cause inward compression of the locking collar.