Abstract: A cylindrical boss portion is press-formed on a baseplate of a disk drive suspension. The boss portion is penetrated by a ball insertion hole relative to the thickness of the baseplate. The baseplate is formed of stainless steel. A chemically-polished surface is formed on an inner circumferential wall of the ball insertion hole by chemically polishing the baseplate after heat-treating it. The boss portion is inserted into a mounting hole of an actuator arm. A ball having a diameter larger than the inside diameter of the ball insertion hole is passed through the ball insertion hole. As the diameter of the boss portion is enlarged by the ball, the boss portion is fixed to the actuator arm.