A pivoting collet chuck - comprising a chuck body in which an accommodating opening is worked into the chuck body and runs centrally in relation to its longitudinal axis, - comprising a pivoting ring inserted in the accommodating opening of the chuck body, on which pivoting ring at least three clamping jaws that can be advanced radially perpendicularly to the longitudinal axis of the chuck body are supported, by means of which a rotationally symmetrical workpiece to be machined is locked in the chuck body centrally in relation to its longitudinal axis, - comprising an advancing device which is inserted into the pivoting ring and by means of which the clamping jaws can be moved synchronously, - comprising two pivot pins (11, 12) which are supported in the chuck body and which form a pivot axis and are in a non-positive or positive active connection with the pivoting ring and - comprising at least one driving means in a driving connection with one of the pivot pins, characterised in that the clamping axes of the clamping jaws run offset to the pivot axis formed by the pivot pins (11, 12), that the advancing device of the at least three clamping jaws is formed by a synchronising ring which is supported so as to be movable parallel to the longitudinal axis of the chuck body in the pivoting ring, that a driving surface extending at an angle to the longitudinal axis of the chuck body is worked onto the synchronising ring in the region of the respective clamping jaw, that a contact surface is provided on the respective clamping jaw, which contact surface interacts with the driving surface of the synchronising ring in such a way that the clamping jaws are moved radially out of the pivoting ring, that the two holding pins located opposite to one another are mounted in the chuck body so as to be radially movable, that the fixation axis formed by the holding pins is offset in relation to the pivot axis and the clamping axes formed by the clamping jaws, preferably running at an angle of 115° in relation to the pivot axis, that two pairs of openings are worked into each pivoting ring, they are aligned in the direction of the chuck body, that in the locking position, the holding pins engage in one of the pairs of openings, that the position of the corresponding holding pin can be established using an electric and/or mechanical monitoring device, and that depending on the position of the holding pins, the movements of the driving means are enabled or blocked. - comprising a chuck body in which an accommodating opening is worked into the chuck body and runs centrally in relation to its longitudinal axis, - comprising a pivoting ring inserted in the accommodating opening of the chuck body, on which pivoting ring at least three clamping jaws that can be advanced radially perpendicularly to the longitudinal axis of the chuck body are supported, by means of which a rotationally symmetrical workpiece to be machined is locked in the chuck body centrally in relation to its longitudinal axis, - comprising an advancing device which is inserted into the pivoting ring and by means of which the clamping jaws can be moved synchronously, - comprising two pivot pins (11, 12) which are supported in the chuck body and which form a pivot axis and are in a non-positive or positive active connection with the pivoting ring and - comprising at least one driving means in a driving connection with one of the pivot pins,