Patent ID: 8172235

Claim:
A chuck mechanism of a striking tool, comprising: a cylindrical tool holder in which a rear end of a bit is inserted from a front end of the holder; two balls which are rollable through a predetermined distance in an axial direction of the tool holder in a pair of accommodation holes provided in the tool holder and are capable of moving through a predetermined distance in a radial direction of the tool holder; a contacting member which is externally mounted on the tool holder to force the balls to respective front positions of the accommodation holes by a forcing means; an operation sleeve which is externally mounted on the tool holder so as to be movable back and forth between a lock position, in which a pressing ring provided at the inner periphery is located on the outside of the balls at the front positions to project the balls radially inwardly from the tool holder, and an unlock position, in which the pressing ring retracts from the outside of the balls at the front positions to allow the balls to retract radially outwardly from the tool holder; and a holding means for holding the pressing ring and the operation sleeve at an advance position, wherein when the rear end of the bit is inserted into the tool holder, each ball is rolled rearward by contact of the rear end of the bit and pushed in between the pressing ring and the contacting member and retracted radially outwardly from the tool holder, in a state where the pressing ring is held at the advance position by the holding means, wherein the contacting member is configured to tilt with respect to an axial direction of the tool holder in response to the rear end of the bit coming into contact with the balls and rolling the balls rearward.