Abstract: A tool actuating mechanism in which first and second main cam shafts are driven by first and second numerically controlled drive means, respectively, and at least one auxiliary cam shaft is selectively engageable with one of the first and second main cam shafts by a clutch means. A plurality of master cams are carried on the first, second and auxiliary cam shafts and a plurality of connecting mechanisms including actuators are associated with the master cams, respectively. The clutch means and the actuators are operable to transmit the motions of selected ones of the master cams carried on the first, second and auxiliary cam shafts to selected ones of a plurality of tool holders, whereby the selected ones of the tool holders are allowed to be concurrently fed toward a workpiece by the first and second drive means at given feed rates.