A chuck for a tool according to the present invention incorporates a clutch mechanism (17) between a rotating member (3) and a rotating nut (4). The clutch mechanism intermittently cuts off the transmission of power from the rotating nut to the rotating member, generating an impact force. This impact force increases the amount of force with which a tool (W) such as a drill is fastened and makes release of the tool smooth. <H0> Abstract </H0> A chuck for tools according to the present invention is provided with a clutch mechanism (17) between a pivotable member (3) and a nut (4) and the transmission of power from the nut to the pivotable member is cut off intermittently by the clutch mechanism. A force for tightening a tool (W), such as a drill, can be increased and the tool can be released smoothly by impact forces produced by the intermittent power transmission cut-off operations.
