A circular cutting unit operable to partially cut a cable along a cutting plane that is perpendicular to a cable axis comprising: a drive disc rotatable about the cable axis; a pair of knife holders mounted to the drive disc, each of the knife holders configured to receive and retain a knife blade ; an adjustment disc rotatable about the cable axis, the adjustment disc including a pair of adjusting elements that each engage one of the knife holders, wherein a relative change in an angle of the adjustment disc relative to the drive disc causes movement of the knife blades in the cutting plane toward or away from each other; and a primary drive assembly operable to rotate the drive disc and the adjustment disc at a cutting speed; an adjustment drive assembly coupled to the adjustment disc, wherein operation of the adjustment drive assembly modifies a rotation speed of the adjustment disc relative to the rotational cutting speed of the drive disc for an adjustment period to create a change in an angle of the adjustment disc relative to the drive disc to cause movement of the knife blades in the cutting plane toward or away from each other; wherein the primary drive assembly includes a drive pulley connected to the drive disc by a first pulley belt and an adjustment pulley connected to the adjustment disc by a second pulley belt , wherein the drive pulley and the adjustment pulley are rotationally coupled to a primary drive shaft rotated at a cutting speed by a primary drive motor , wherein the adjustment drive assembly is coupled to the adjustment pulley , wherein the adjustment drive assembly is operable to modify the rotational speed of the adjustment pulley, characterized in that the primary drive shaft includes a spiral groove , and the adjustment drive assembly includes a ball nut movable along the spiral groove . a drive disc rotatable about the cable axis; a pair of knife holders mounted to the drive disc, each of the knife holders configured to receive and retain a knife blade ; an adjustment disc rotatable about the cable axis, the adjustment disc including a pair of adjusting elements that each engage one of the knife holders, wherein a relative change in an angle of the adjustment disc relative to the drive disc causes movement of the knife blades in the cutting plane toward or away from each other; and a primary drive assembly operable to rotate the drive disc and the adjustment disc at a cutting speed; an adjustment drive assembly coupled to the adjustment disc, wherein operation of the adjustment drive assembly modifies a rotation speed of the adjustment disc relative to the rotational cutting speed of the drive disc for an adjustment period to create a change in an angle of the adjustment disc relative to the drive disc to cause movement of the knife blades in the cutting plane toward or away from each other; wherein the primary drive assembly includes a drive pulley connected to the drive disc by a first pulley belt and an adjustment pulley connected to the adjustment disc by a second pulley belt , wherein the drive pulley and the adjustment pulley are rotationally coupled to a primary drive shaft rotated at a cutting speed by a primary drive motor , wherein the adjustment drive assembly is coupled to the adjustment pulley , wherein the adjustment drive assembly is operable to modify the rotational speed of the adjustment pulley, characterized in that the primary drive shaft includes a spiral groove , and the adjustment drive assembly includes a ball nut movable along the spiral groove . <EOS>