Abstract: A chuck of the indexing type is comprised of a chuck housing, a pair of opposed jaw supports mounted within the housing with one of the supports being fixedly secured thereto and the other of the supports including an inclined cam surface and being movable toward and away from the fixed support. A jaw is mounted on each support through a live center and rotates relative to the support into any one of a number of indexed positions. A hydraulic jaw operator mounted on the housing includes a wedge drive engaging the cam surface of the movable support for driving the movable support and its associated jaw toward and away from the fixed support. Another feature of the invention is the provision for index locking means for each jaw mounted on the housing for locking the jaws against rotation.