Drill with a centering drill insert, and a method of using a drill with a centering drill insert, and the insert therefor

A drilling insert for use on a drill 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;
• usaid inner lip being structured to be 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;
• and
• said protuberance comprises a convex, rounded tip portion disposed between and connecting said inner protuberance lip and said outer protuberance lip.

A drill comprising a shank portion, a fluted portion, and a cutting insert, said 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 a 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 is configured and disposed to compensate for radial forces acting on said drill during drilling to minimize radial drifting of said drill;
• said protuberance comprises an inner lip and an outer lip;
• said inner lip of said protuberance is 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 is 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;
• and said protuberance comprises a convex, rounded tip portion disposed between and connecting said inner protuberance lip and said outer protuberance lip.

A method of drilling a hole in workpiece using a drill comprising a shank portion, a fluted portion, and a cutting insert, said 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 a 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;
• and 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 comprising an inner lip and an outer lip;
• said inner lip of said protuberance is 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;
• said outer lip of said protuberance is 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;
• 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;
• and said protuberance comprises a convex, rounded tip portion disposed between and connecting said inner protuberance lip and said outer protuberance lip, said method comprising the steps of:
• disposing said cutting insert adjacent the central longitudinal axis of said drill to permit said cutting insert to cut a central portion of a hole;
• drilling into a workpiece with said cutting insert;
• and
• compensating for radial forces acting on said drill during drilling with said protuberance to minimize radial drifting of said drill.

A drilling insert for drilling a hole, the drilling 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 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 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;
• and
• said protuberance comprises a convex, rounded tip portion disposed between and connecting said inner protuberance lip and said outer protuberance lip.