Drill with discontinuous cutting lips

Claim 1

A drill for boring a smooth-walled burr-free hole comprising a body having discontinuous cutting lips formed at one end thereof, the cutting lips each extending generally from a tip substantially at the axis of rotation of the drill to the peripheral edge thereof, the cutting lips each being recessed intermediate the length thereof at a distance spaced from the tip, each recess being defined by a first surface extending inwardly from the cutting lip toward the axis of the drill to provide axial relief and a second surface extending rearwardly from the cutting lip with respect to the direction of rotation of the drill and intersecting the said first surface, the second surface being relieved rearwardly from the cutting lip, the portion of each cutting lip remote from the tip and on the opposite sides of the recess being formed along a curve extending to tangentially engage and join both the periphery of the drill body and a line defined by the included angle of the straight cutting lips normally formed on conventional drills for most efficient drilling, whereby in operation, heat generated during drilling is better dissipated and a burr-free hole to the desired diameter is formed.