Drilling and threading tool and method for drilling and threading

A combined drilling and threading tool comprising a shank having a forward end defined by a conical front portion which includes a plurality of hole-cutting edges, said hole-cutting edges extending symmetrically from adjacent a central front-to-rear extending axis of rotation of said shank, said shank including clearance surface means extending rearwardly of radially inner portions of said cutting edges, a plurality of ribs disposed rearwardly of respective ones of said hole-cutting edges, said ribs being spirally curved in said front-to-rear direction and extending symmetrically relative to said axis, said ribs being spaced apart by chip flutes extending symmetrically relative to said axis, each rib including leading and trailing edges with respect to a direction of rotation of said tool, a plurality of thread-cutting teeth spaced along each of said ribs in said front-to-rear direction, said teeth on each rib being spaced apart by equal distances in said front-to-rear direction, each of said teeth including a thread-cutting edge disposed at said leading edge of its associated rib and side surface means extending from said thread-cutting edge in a direction opposite said direction of rotation, each of said cutting edges including edge portions converging toward a point, said teeth of each rib being circumferentially aligned with associated teeth of the other ribs such that said points on circumferentially successive ribs lie substantially within a common plane disposed perpendicularly to said axis, each said tooth having an axial dimension in a direction parallel to said axis, said axial dimension decreasing in size away from said direction of rotation, each of said teeth having a radial dimension extending radially relative to said axis, said radial dimension decreasing in size away from said direction of rotation, each of said teeth terminating at a location intermediate said leading and trailing edges of its associated rib.