Abstract: A compensating nail-driving chuck uniformly countersinks nails into boards, despite variations in thickness and hardness of the boards. The nail-driving chuck has a chuck body with jaws at the lower end for holding a nail. A hydraulic cylinder has a drive rod which is connected to a drive pin for driving the nail out through the jaws and into the board. The chuck body is movable with the drive rod until a surface of the board is engaged. At that point, movement of the chuck body stops, and relative movement of the drive rod and drive pin with respect to the chuck body begins. The chuck body limits the stroke of the drive rod, so that the nail is driven a uniform distance into the board once the surface of the board has been engaged.