Importance

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Abstract

Drill bit for drilling holes of different diameters which has a series of cylindrical outer surfaces of increasing diameter from the outer to the inner end of the drill bit. A beveled conical surface interconnects each adjacent pair of cylindrical surfaces. At least two flutes are machined at two circumferentially spaced locations to provide two cutting edges on each diameter of the drill. At each cutting edge the cylindrical surfaces are relieved radially and the conical surface is relieved axially over an acute circumferential angle. The major peripheral portions of the cylindrical and conical surfaces for each diameter are respectively concentric to the axis of the drill and of zero pitch angle.

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First Claim