Abstract: A ball nose cutter having a replaceable single cutter insert in which the cutting edges thereof include a pair of mutually spaced apart cutting tips, one cutting tip at a time being selected for use by being located at the centerline of rotation of the ball nose cutter. The cutter insert is of circular cross-section for rotatably seating within a circularly cross-sectioned groove in a cutter body. A bore in the cutter insert is aligned with an off-axis threaded bore in the cutter body so that a holder screw which passes therethrough threadably holds the cutter insert with respect to the cutter body. A planar face is provided adjacent each cutting edge, wherein each planar face has an orientation so that the selected cutting tip is exactly located on the centerline rotation of the ball nose cutter.

Abstract: Improvement in a machine tool center device having a hollow body and a center shaft therein, the shaft having a conical front end, a bearing between the body and shaft for moveably supporting the latter, the improvement comprising a center device which has an arrangement for converting the same from a live center to a dead center and vice versa, an arrangement for supporting the shaft in the body for both rotation and reciprocation in respect thereto, the conversion arrangement preventing rotation of the shaft while permitting reciprocation thereof, the conversion arrangement being accessible from the exterior of the body for insertion or removal in respect thereto, a yieldable mechanism in the body operative upon the shaft for urging the front end outwardly of the body, a thrust cap rotatably carried on the front end of the body having an aperture therein through which the front end projects, the thrust cap being held fast against reciprocative movement relative to the body, a nose cap carried on the thrust