Rotary-head machining unit

A rotary head machining unit that carries at least two pivoting tools to machine a non-rotary part centered on a rotational axis of the rotary head, including a frame (2) on which a rotor (1) is mounted, carried by two external bearings (3), said rotor (1) having an axial channel and, coupled to rotational drive means (12 and 15), axial guiding means for said non-rotary part (22 and 24), the axial guiding means being carried by bearings (21) in said rotor (1) and by fixed support (23), means for holding and moving said non-rotary part axially, at least two tool holders (4a-4c) mounted in said rotary head in order to pivot about respective axes parallel to the rotational axis, each of the at least two tool holders comprising a control lever (4j-41) arranged transversally, pivoting control means cooperating with said control lever and comprising a control element (14) that is movable in axial translation in the rotor and coupled to a translation control device, and pairs of pusher elements arranged respectively on each of the control levers and on the corresponding control element, each of the pairs of pusher elements comprising a guiding surface (4d-4f) and a pushing surface (20) resting against the guiding surface in a position that varies according to the translation of said control element (14), said guiding surface (4d-4f) being located on the tool holder and the corresponding pushing surface (20) being located on said control element (14), and every guiding surface corresponding to a pivoting tool holder having the shape of a helix portion whose axis coincides with the pivoting axis of said tool holder, wherein said control element is a control bush (14) mounted coaxially on a spindle, said control bush (14) being arranged to slide axially and to be in a first advanced position, in a second retracted position, said control bush (14) carrying at one end thereof a control surface with an ellipsoidal shape (20) arranged to cooperate with said helical guiding surfaces (4d-4f) and to make the pivoting tools plunge, means for moving said control bush (14) axially and a phase shift device arranged to bring said control bush (14) in two, three or four predetermined angular positions about its axis.