A lathe to simultaneously machine two or more die molds in chucks of a headstock at one end of a bed used to support a saddle which is moved along a bed by a feed screw parallel to the rotational axes of the chucks. A drive in the headstock also rotates a master mold about a horizontal axis at a laterally-disposal location from the die molds. A probe provides a signal corresponding to the internal surface contour in the master mold to move cutting bars which always extend in a generally-parallel relation with the rotational axes of the chucks during machining of the die molds. A first swivel is carried by a cross slide upon the saddle. The first swivel is adjustable about a vertical axis to provide a desired angle between the direction of attack by the cutting bars and the horizontal axes of rotation by the chucks. A linear displacement assembly is supported by the first swivel and includes a movable member which is reciprocated by a piston and cylinder assembly for displacing the cutter bars according to the output signal from the tracer probe. A second swivel is supported by the movable member of the linear displacement members to angularly position tool support bars so that the bars extend in a generally-parallel relation with the horizontal axes. The tracer probe carried by a follower bar is supported by a swivel frame which is supported by the second swivel so that the follower bar extends in a generally-parallel relation with the cutter bars.