Abstract: A chuck system for machine tools with a rotating jaw chuck has clamping jaws of the jaw chuck which can be radially adjusted relative to an axis of rotation. The clamping jaws are displaceably mounted in a bearer connected with a drive shaft, and in which engagement openings for the introduction of an adjustment tool for the positioning of the clamping jaws are arranged in the region of the bearer. The bearer is surrounded by a protective sheath that is guided so as to be displaceable in the direction of the axis of rotation. The protective sheath comprises through openings, which are arranged so as to be congruent to the engagement openings in a handling position of the protective sheath, and are arranged so as to be offset to the engagement openings in an operating position of the protective sheath. In the operating position, the clamping jaws are radially surrounded, at least in regions, by the protective sheath.