The invention concerns a self-penetrating drilling method and a thrust-generating tool: the tool comprises N blades. Each blade comprised K drill cutters. The shapes, positions and orientations of said drill cutters are determined in the following manner: the k.sup.th drill cutter of the last blade drills, at the (q-1).sup.th of the tool rotational cycle, a cut in the rock downstream of the one produced by the (k+1).sup.th drill cutter of the first blade at the q.sup.th rotational cycle of the tool; the k.sup.th drill cutter of the nth blade drills, at the q.sup.th rotational cycle of the tool, a cut in the rock downstream of the one produced by the k.sup.th drill cutter of the (n+1).sup.th blade at the q.sup.th rotational cycle of the tool; the normal to the leading edge of the drill cutter has a component along the axis of rotation oriented towards upstream.
A rolling cone drill bit including multiple cones with regions of intermeshing and non-intermeshing cutter elements. In the non-intermeshed regions, an array of cutter elements is disposed about the cone surface in a non-circumferential arrangement with the cutter elements being mounted at differing radial distances from the bit axis. This non-circumferential arrangement, which may be a spiral, multiple spirals, other patterns of offset cutter elements, or a random arrangement, provides a composite cutting profile having substantial width and bottomhole coverage and is free of ridge-producing voids. In certain embodiments, the composite cutting profiles of the arrays at least partially overlap, and may be arranged to cover a portion of or the entire non-intermeshed region on the cones.
