a drilling apparatus includes a tubular body including an upper connection and a lower connection with a drill bit disposed thereon , and an axial borehole therethrough , wherein the upper connection is configured to attach to a drillstring , primary cutter blocks coupled to the tubular body and configured to selectively expand radially therefrom . the drilling apparatus further includes backup cutter blocks coupled to the tubular body and configured to selectively expand radially therefrom , and an activation system configured to selectively expand and collapse the primary and backup cutter blocks in response to changes in weight applied to the primary and backup cutter blocks .