Devices (10) for burnishing a surface (111, 112) on an object (108) includes a body (11) having a passageway (25), an accumulator piston (65) mounted on the body for sealed sliding movement within the passageway, a coarse adjustment screw (13) mounted on the body, a resilient member (14) acting between the coarse adjustment screw and the accumulator piston, a lever (12) mounted on the body, a chamber (32) communicating with the accumulator piston, an actuator piston (78) mounted on the body for sealed sliding movement within a cylindrical opening (41) toward and away from the rearward portion (48) of the lever, and a roll (15) rotatably mounted on the forward portion (49) of the lever. The devices are adapted to be mounted on a machine tool (105) and moved toward the object to burnish the surface with controllable force along the required length of the surface.