Abstract: A tool chuck has a plurality of inclined chuck claws mounted centrally of a forward end of a chuck body to be slidable toward and away from one another, a nut ring meshed with the chuck claws and rotatable to screw-feed the chuck claws toward and away from one another, and a torque amplifying mechanism interposed between the nut ring and a control ring fitted to an outer peripheral surface of the chuck body, whereby the control ring is turned directly by hand to cause the chuck claws to hold a tool. A torque limiter is incorporated into the torque amplifying mechanism for allowing the tool to be clamped by a force not exceeding a predetermined value. Excessive tightening of the tool is thereby avoided so that the tool is removable when desired, and at the same time the above torque limiter is formed compact.