Rotary cutting tool

A rotary cutting tool comprising:

• a cutting portion;
• said cutting portion comprising a tip portion and a fluted portion;
• said tip portion being configured to cut an orifice having a first diameter in an object to be cut;
• said cutting portion defining a central longitudinal axis disposed through said cutting portion;
• said fluted portion comprising a cutting edge configured to cut an orifice having a final diameter;
• said final diameter orifice being greater than said first diameter orifice cut by said tip portion of said rotary cutting tool;
• said fluted cutting edge comprising a first edge portion and a second edge portion;
• said first edge portion comprising a first edge area, a second edge area, and a third edge area;
• said first edge area being disposed at a first longitudinal distance measured along said central longitudinal axis from said tip portion;
• said second edge area being disposed at a second longitudinal distance measured along said central longitudinal axis from said tip portion;
• said third edge area being disposed at a third longitudinal distance measured along said central longitudinal axis from said tip portion;
• said second longitudinal distance being greater than said first longitudinal distance;
• said third longitudinal distance being greater than said second longitudinal distance;
• said first edge area being disposed at a first radial distance from said central longitudinal axis;
• said first radial distance being measured radially from said central longitudinal axis;
• said second edge area being disposed at a second radial distance from said central longitudinal axis;
• said second radial distance being measured radially from said central longitudinal axis;
• said third edge area being disposed at a third radial distance from said central longitudinal axis;
• said third radial distance being measured radially from said central longitudinal axis;
• said tip portion comprising a peripheral area;
• said peripheral area being disposed at a radial distance (HR) being measured radially from said central longitudinal axis;
• said second radial distance (MR), of said second edge area, being greater than all of (i), (ii), and (iii), wherein (i), (ii), and (iii) are:
• (i) said first radial distance, of said first edge area;
• (ii) said third radial distance, of said third edge area;
• and
• (iii) said radial distance (HR), of said tip portion;
• said first edge area having a first length measured along said central longitudinal axis;
• said second edge area having a second length measured along said central longitudinal axis;
• said third edge portion having a third length measured along said central longitudinal axis;
• the sum of the lengths of said first edge area, said second edge area, and said third edge area being substantially greater than the difference between said second radial distance (MR), of said second edge area, and said radial distance (HR), of said tip portion;
• and
• wherein said rotary cutting tool has at least two cutting edges that respectively comprise a main cutting edge and that respectively are disposed symmetrically with respect to the central axis (M) of a cutter portion, whereby the radius (HR) of the main cutting edges is less than the maximal cutting edge radius (MR) of the cutter portion;
• at least one secondary cutting edge is associated with a main cutting edge, said secondary cutting edge is curvilinear in at least a portion and is configured as smooth finishing cutting edge, said secondary cutting edge comprises a plurality of curve-forming radii (R1,R2,R3), whereby in an outer smooth finishing region within the region of the maximal cutting edge radius (MR), the curve-forming radius (R2) of the smooth finishing cutting edge is at least as large as the maximal cutting edge radius (MR);
• the cutter portion that is adjacent to the outer smooth finishing region is tapered to be diminished in size in the direction away from the main cutting edges.

A rotary drill bit configured to drill a hole in an object to be drilled, said drill bit having a central longitudinal axis and comprising:

• a tip portion being configured to cut a hole in an object;
• said tip portion comprising at least one chisel edge;
• a fluted portion having at least one chip flute disposed along said central longitudinal axis;
• said fluted portion comprising at least one land surface adjacent said at least one chip flute;
• said at least one land surface and its corresponding chip flute forming an edge, a portion of which is a cutting edge;
• said cutting edge portion of said fluted portion being configured and disposed to further cut and enlarge the diameter of a hole cut by said tip portion, and to form a smoother finish on the interior surface of the hole than the finish formed by said tip portion;
• said cutting edge portion of said fluted portion being configured and disposed to bulge outwardly in a radial direction away from said central longitudinal axis to form a bulge on said fluted portion, which bulge extends radially beyond said tip portion;
• said cutting edge portion of said fluted portion comprising at least one outwardly curved and convex finishing portion;
• and
• said cutting edge portion comprising a point which, measured radially from said central longitudinal axis, is the outermost point of the exterior surface of said fluted portion.