Rotary cutting head having a rigid mounting protuberance and rotary cutting tool

A rotary cutting tool (52, 152) comprising:

• a tool shank (54, 154) extending along a second axis (A2) and having a head receiving pocket (56) formed at a forward end thereof, the head receiving pocket (56) comprising a shank support surface (60) transverse to the second axis (A2) and a central recess (62) formed in the shank support surface (60), wherein:
• the central recess (62) has N circumferentially spaced apart abutment portions (72),
• each abutment portion (72) has a radially inward facing abutment surface (74), and
• N is an integer greater than 1;
• and
• a cutting head (20, 120) releasably secured to the head receiving pocket (56), the cutting head being rotatable about a first axis (A1) in a first direction of rotation (R1), and comprising:
• a cap portion (22) having N cutting portions (26) circumferentially alternating with N head chip flutes (28), and a head base surface (30) facing in an axial rearward direction (DR);
• and
• a rigid mounting protuberance (24) joined to the cap portion (22) and extending axially rearwardly from the head base surface (30), the mounting protuberance (24) exhibiting N-fold rotational symmetry about the first axis (A1), and having N circumferentially spaced apart convex clamping surfaces (38), each clamping surface (38) bisected by a radial clamping bisector plane (PB) containing the first axis (A1),
• wherein:
• the N cutting portions (26) define a cutting diameter (DC) corresponding to a cutting circle (CC),
• the N clamping surfaces (38) is equal in number to the N cutting portions (26),
• in a cross-section taken in a first plane (P1) perpendicular to the first axis (A1) and intersecting the cap portion (22), the N head chip flutes (28) are inscribed by an imaginary first circle (C1) having a first diameter (D1) at N radially innermost head flute points (NH), and
• in a cross-section taken in a second plane (P2) perpendicular to the first axis (A1) and intersecting the mounting protuberance (24), the N clamping surfaces (38) are circumscribed by an imaginary second circle (C2) having a second diameter (D2),
• and wherein:
• the first diameter (D1) is greater than the second diameter (D2), and
• the second diameter (D2) is less than forty percent of the cutting diameter (DC);
• wherein in an assembled position:
• the head base surface (30) contacts the shank support surface (60) or a plurality of shoulder surfaces (82) offset therefrom,
• the second axis (A2) is coincident with the first axis (A1), and
• the mounting protuberance (24) is clampingly retained in the central recess (62), with the N clamping surfaces (38) make clamping contact with the N abutment surfaces (74), and
• apart from the N clamping surfaces (38) making clamping contact with abutment surfaces (74), no other portion of the mounting protuberance (20) contacts the central recess (62).

A cutting head (20, 120) rotatable about a first axis (A1) in a first direction of rotation (R1), and comprising:

• a cap portion (22) having N cutting portions (26) circumferentially alternating with N head chip flutes (28), a head base surface (30) facing in an axial rearward direction (DR), and the N head chip flutes (28) intersecting the head base surface (30);
• and
• a rigid mounting protuberance (24) joined to the cap portion (22) and extending axially rearwardly from the head base surface (30), the mounting protuberance (24) exhibiting N-fold rotational symmetry about the first axis (A1), and having N circumferentially spaced apart convex clamping surfaces (38) and N joining surfaces (40) circumferentially alternating with the N clamping surfaces (38), each clamping surface (38) bisected by a radial clamping bisector plane (PB) containing the first axis (A1), and each joining surface (40) intersecting two circumferentially adjacent clamping surfaces (38),
• wherein:
• N is an integer number greater than 1,
• the N cutting portions (26) define a cutting diameter (DC) corresponding to a cutting circle (CC),
• the N clamping surfaces (38) is equal in number to the N cutting portions (26),
• each cutting portion (26) has a single cutting edge (34) associated therewith, such that the cutting head has a total of N cutting edges, a total of N cutting portions and a total of N clamping surfaces;
• in a cross-section taken in a first plane (P1) perpendicular to the first axis (A1) and intersecting the cap portion (22), the N head chip flutes (28) are inscribed by an imaginary first circle (C1) having a first diameter (D1) at N radially innermost head flute points (NH), and
• in a cross-section taken in a second plane (P2) perpendicular to the first axis (A1) and intersecting the mounting protuberance (24), the N clamping surfaces (38) are circumscribed by an imaginary second circle (C2) having a second diameter (D2),
• and wherein:
• the first diameter (D1) is greater than the second diameter (D2), and
• the second diameter (D2) is less than forty percent of the cutting diameter (DC).