A method of two-phase atherectomy for removal of plaque within an artery forming a stenosis including a first phase of rotational drilling by exerting a rotational force on a cutter to form a channel within the plaque having a diameter substantially equal to a diameter of the cutter—the cutter being rotated at a first rotational speed sufficient to maintain rotation of the cutter about a stationary rotational axis—and a second phase of orbital impact by exerting a rotational force on the cutter to result in radial orbital motion of the cutter within the channel resulting in periodic impact of the cutter upon the plaque to form micro-fractures within the plaque and enlarge the diameter of the channel to a diameter substantially greater than the diameter of the cutter—the cutter being rotated at a second rotational speed to result in the radial orbital motion of the cutter.