Patent ID: 8475090
Filing Date: 2013-07-02
Classification: B23B,Y10T

Abstract:
1. A drill for drilling a hole in an object, said drill having a central longitudinal axis, said drill comprising: a shank portion being configured to be gripped by a tool; a fluted portion comprising two chip flutes and a tip; an inner cutting insert and an outer cutting insert; said inner cutting insert being disposed at said tip adjacent the central longitudinal axis of said drill; said outer cutting insert being disposed at said tip adjacent the periphery of the drill a distance from the central longitudinal axis of said drill; said inner cutting insert being configured and disposed to cut a central portion of a hole; said outer cutting insert being configured and disposed to cut an outer portion and side wall of a hole; said outer cutting insert comprising a cutting edge which is straight; said inner cutting insert comprising a central body portion and at least one angular cutting edge disposed on the periphery of said central body portion; said angular cutting edge comprising an inner lip and an outer lip being disposed at an angle with respect to one another, wherein a line extending along and from said inner lip intersects with a line extending along and from said outer lip at the vertex of the angle; said inner lip being disposed closer to the central longitudinal axis of said drill than said outer lip; said angular cutting edge comprising a protuberance being disposed between and connecting said inner lip and said outer lip; said protuberance being disposed to project outwardly away from said central body portion beyond the vertex of the angle defined by the intersection of the lines extending from said inner lip and said outer lip; said protuberance being configured and disposed to compensate for radial forces acting on said drill during drilling to minimize radial drifting of said drill; said protuberance comprising an inner lip and an outer lip; said inner lip of said protuberance being connected to said inner lip of said cutting edge and forming a smooth curvilinear transition between said inner lip of said protuberance and said inner lip of said cutting edge; and said outer lip of said protuberance being connected to said outer lip of said cutting edge and forming a smooth curvilinear transition between said outer lip of said protuberance and said outer lip of said cutting edge, wherein: said inner protuberance lip and said outer protuberance lip are disposed at an angle with respect to one another, which angle is smaller than the angle defined by said inner lip and said outer lip; said protuberance comprises a convex, rounded tip portion disposed between and connecting said inner protuberance lip and said outer protuberance lip; one of (A) and (B): said cutting insert comprises a flank surface disposed along said cutting edge; said flank surface comprises a clearance area disposed adjacent to said protuberance; said cutting insert comprises an indexable insert comprising at least two cutting edges; said cutting insert is seated in an insert seat in said drill; said insert seat comprises a corner hole disposed between two insert bearing faces; and said protuberance of an inactive cutting edge is inserted into said corner hole to center said cutting insert in said insert seat and to fill said corner hole to prevent entry of chips into said corner hole during drilling.