Abstract: An article feeder has a base and a frame mounted on the base with a bowl, which receives and dispenses articles, secured to the frame. The frame and bowl assembly constitute one mass of a two mass system, and the base constitutes the other mass of the system. Several sets of leaf springs are secured by clamps between the frame and the base to support the frame and bowl for rotational oscillation by a motor mounted on the base. The sets of leaf springs provide the total spring coupling between the frame and bowl assembly and the base. These sets of leaf springs are supported adjacent one clamped end thereof by adjustable supports that can alter the effective lengths of the leaf spring sets to change the torsional natural frequency of the two mass system in small increments without disturbing the clamps mounting the sets of leaf springs.