COMPLEX NC LATHE

PURPOSE:To uniform the roughness on a machined face by providing a means for controlling the load of a tool motor indexed to a machining position and comparing the detected load with a proper set value to control the push-in amount of a rotary tool or a rotary tool unit, thereby enabling buffing work with a constant pressing force. CONSTITUTION:When buff work is carried out through an outer diameter buff, an outer diameter buff tool unit 20 is mounted on a pot 12 to make indexing to a working position, then a tool rotation motor 13 is driven through a command of an NC machine 10 to rotate a buff grinding wheel 22. Feed motors 5, 7 for screws 6, 8 are driven based on a command of the NC machine 10 to control movement of turret cutter table 9 in X and Y directions and contacts the outer circumferential face of the buff grinding wheel 22 with the outer circumference of a work W. Buff machining load produced through the contact is detected through a load detecting circuit 25 then the detected value is compared with a proper set value P in a comparator 26, and the command value is regulated to maintain the load at a constant level thus controlling driving of a tool rotation motor 13 through a drive circuit 27.