Cutting head having tip portion with radially extending front cutting edges provided with both negative and positive rake angles, and rotary cutting tool

A cutting head (20) rotatable about a first axis (A1) in a direction of rotation (DR), and comprising:

• an intermediate portion (22) having an integer number N, N≥2 circumferentially spaced apart peripheral surfaces (26), each peripheral surface (26) having a leading edge (28), and the plurality of leading edges (28) defining a cutting diameter (DC);
• and
• a tip portion (24) having an axially forwardmost tip point (NT) contained in the first axis (A1) and N front surfaces (30), each front surface (30) having a radially extending front cutting edge (31) which comprises an outer cutting edge (32) extending radially inwardly from one of the leading edges (28) and an inner cutting edge (34) extending radially inwardly from said outer cutting edge (32), each inner cutting edge (34) adjoining its associated outer cutting edge (32) at a cutting edge transition point (NR),
• wherein:
• in a cross-section taken in a first vertical plane (PV1) parallel to the first axis (A1) and intersecting any one of the outer cutting edges (32), an outer rake surface (40) adjacent to said outer cutting edge (32) is inclined at a positive outer rake angle (α1);
• and
• in a cross-section taken in a second vertical plane (PV2) parallel to the first axis (A1) and intersecting any one of the inner cutting edges (34), an inner rake surface (42) adjacent to said inner cutting edge (34) is inclined at a negative inner rake angle (α2),
• wherein:
• each outer rake surface (40) is disposed on a head flute (44) extending axially rearwardly from the tip portion (24) and intersecting one of the leading edges (28);
• and
• each inner rake surface (42) is disposed on a gash (46) extending axially rearwardly from the tip portion (24) and intersecting one of the head flutes (44),
• and wherein:
• each gash (46) has a gash path (GP) defined by a plurality of gash apex points from a series of cross-sections taken in planes perpendicular to the first axis (A1) and intersecting the gash (46) along its axial extent;
• each gash path (GP) extends to a gash path end point (NP) located a first distance (d1) axially rearward of the tip point (PT);
• and
• the first distance (d1) is greater than thirty percent of the cutting diameter (DC).