Surface decarburization of a drill bit

A microdrill, comprising:

• a drill body having a cutting tip, an axis of symmetry, and a plurality of flutes wherein said flutes have a rake surface at said cutting tip;
• said cutting tip comprising a plurality of side blades between said flutes and joined at a web, a plurality of flank surfaces extending from an outer diameter of said cutting tip to said axis of symmetry, and a plurality primary cutting edges at the intersection of said flank surfaces with said rake surfaces which have a plurality of outer surfaces;
• wherein said primary cutting edges include an angular surface formed on the forward end of said rake surfaces;
• wherein said primary cutting edges comprise a hardened layer formed from the outer surface of the microdrill.

A drill, comprising:

• a drill body having a cutting tip, an axis of symmetry, and a plurality of flutes wherein said flutes have a rake surface at said cutting tip;
• said cutting tip comprising a plurality of side blades between said flutes and joined at a web, a plurality of flank surfaces extending from an outer diameter of said cutting tip to said axis of symmetry, and a plurality primary cutting edges at the intersection of said flank surfaces with said rake surfaces;
• wherein said rake surface and said flank surface are positioned such that an extension of said rake surface intersects an extension of said flank surface at an intersection;
• wherein said primary cutting edges include an angular surface formed on the forward end of said rake surfaces;
• wherein said angular surface is located such that the length of said extension of said rake surface measured between said angular surface and said intersection is a first predetermined value and the length of said extension of said flank surface measured between said angular surface and said intersection is a second predetermined value;
• wherein said first and second predetermined values are equal.

A microdrill, comprising:

• a drill body having a cutting tip, an axis of symmetry, and a plurality of flutes wherein said flutes have a rake surface at said cutting tip;
• said cutting tip comprising a plurality of side blades between said flutes and joined at a web, a plurality of flank surfaces extending from an outer diameter of said cutting tip to said axis of symmetry, and a plurality primary cutting edges at the intersection of said flank surfaces with said rake surfaces;
• wherein said rake surface and said flank surface are positioned such that an extension of said rake surface intersect an extension of said flank surface at an intersection;
• wherein said primary cutting edges include an angular surface formed on the forward end of said rake surfaces;
• wherein said angular surface is located such that the length of said extension of said rake surface measured between said angular surface and said intersection is a first predetermined value and the length of said extension of said flank surface measured between said angular surface and said intersection is a second predetermined value;
• wherein said first and second predetermined values are equal.