Axially supported boring tool and method for making same

Claim 1

A drill bit comprising a cutter blade assembly including a hub, cutter blades extending radially outward from said hub and adapted to cut a circular hole in work upon application of said bit to such work, a cylindrical skirt defining a cylindrical surface, said cutter blades each having one end thereof located in a surface common to said skirt cylindrical surface with said skirt cylindrical surface being in the line of angular travel of the one ends of such cutter blades for stabilizing said bit axially of the desired hole during a drilling operation, said cylindrical skirt having a pair of chip openings defined therein one chip opening being located adjacent each cutter blade and extending through said skirt at an angle to the longitudinal centerline of said skirt, said chip opening forming edges of said skirt, the angular orientation of said chip opening causing the trailing portion of one edge to overlap the leading portion of the other edge to provide the equivalent of a complete cylindrical surface in maintaining stability of said bit during drilling, radius segments radiating laterally from said cutter blades and being integrally attached to said skirt for approximately half the circumference of said skirt, spurs depending from said skirt to a point below said radius segments and with their outer surfaces common to said skirt surface, and guiding means for guiding the drill bit through a material in the axial direction of the drill bit, said guiding means including a pilot attached to said hub and having threads defined thereon for drawing the drill bit into material to be drilled, and threads defined on the outer surface of said skirt, said threads being fewer in number per inch than the threads in said pilot, and engaging the sides of a hole being made in the material by the drill bit to advance the drill bit axially through the hole.