Counterbalanced mechanism for a jaw chuck. There is provided for an otherwise conventional multi-jaw chuck suitable mechanism for independently balancing each said jaw. In a preferred embodiment, a pin is pivotally fixed at one of its ends into each master jaw, pivoted to the chuck body intermediate its ends and pivotally related at its other end to a radially movable counterbalancing mass. Each said mass and jaw are so related to the lever pin upon which they operate that they create balancing moments when the centrifugal force acting on each is equal and, due to the geometry of the apparatus, said moments remain sufficiently close to equal at any speed of operation of the chuck that a substantial balancing of the parts is obtained. Thus, whether the chuck is inside gripping or outside gripping, it can be properly adjusted in a normal manner at a standstill and the pressure of the chuck onto the workpiece will not materially change within the range of any normal operating speed.