Drill chuck for percussion drilling

Chuck for a drilling device for use as a rotary drilling device or a rotary/percussion device, such as a hammer drill, comprising means forming a chuck housing having a central axis and arranged to receive the shank of a drilling tool removably mounted in said chuck and extending generally along the central axis, clamping jaws radially adjustably mounted in said chuck housing means and arranged to be circumferentially spaced apart around the shank of the drilling tool, each said clamping jaw has a radially inwardly facing clamping surface shaped concavely in the circumferential direction around the central axis, at least one projection on each said clamping jaw extending radially inwardly from said clamping surface, said projections extending in the axial direction of the central axis and arranged to engage in recesses in the shank of the drilling tool, wherein the improvement comprises that the clamping surface of each clamping jaw has first guide surfaces extending in the axial direction along the opposite axial extending sides of said projection and at least one second guide surface section extending transversely of the axial direction of the central axis along one of the ends of said projection spaced apart in the axial direction of the chuck.