Abstract: For the change of tools of machine tool operating units, a device is provided which comprises a tool-holder support or carriage (144,204) on which there are mounted at least two tool-holder spindles (48,148) with a corresponding tool (50,150), and the axis of at least one of these at least two tool-holder spindles is inclined at a predetermined angle relative to the axis of the spindle (10,110) of the operating unit. Means controlled by the spindle (10,110) of the operating unit pivot this support or carriage (44,204) and the corresponding at least one tool-holder spindle (48,148) by this predetermined angle, in order to position the required tool-holder in axial alignment with this spindle (10,110).

Abstract: In a transfer machine tool with a rotary table, the machining units with horizontal axes are arranged in orientations which do not coincide with the radii of the rotary table and the workpieces being machined are mounted on piece-holder plates which are fixed to the rotary table but are rotatable about vertical axes perpendicular to the plane of the rotary table; for each advance of a workpiece being machined from one work station to the next, the respective plate is rotated through an angle of between 0.degree. and 45.degree. relative to the radius at the next station, the angle possibly being added algebraically to the angle of rotation necessary when the face of the workpiece to be machined is changed.