Abstract: In construction of a tool chuck in which manual rotation of an outer operation sleeve causes concurrent rotation of an inner screw ring to move clamping jaws in a chuck body following the principle of screw feeding, a solid lubrication coating layer is interposed between the screw ring and the chuck body so as to minimize friction between the two elements during their relative rotation for clamping a tool via the jaws, thereby effectively utilizing input torque from the operation sleeve for clamping operation. The solid lubrication coating layer may be applied either to a washer or directly to the screw ring.

Abstract: In construction of a keyless tool chuck in which clamping torque is transmitted from a manually rotatable operation sleeve on a chuck body to tool clamping jaws in the chuck body via a power transmission unit including a cycloidal gear arrangement, an elastic impulsion sleeve is inserted between the operation sleeve and the chuck body so that elastic compressive deformation of the impulsion sleeve at forced rotation of the operation sleeve causes impulsive meshing engagement in the cycloidal gear arrangement to provide impulsive clamping force on a tool clamped by the jaws. Resultant clamping force is at least twice as large as that provided by a conventional cycloidal gear arrangement only.