Rotary cutting head having a rigid mounting protuberance and rotary cutting tool
A cutting head rotatable about a first axis, has a cap portion and a rigid mounting protuberance joined thereto. The cap portion has a plurality of cutting portions circumferentially alternating with a plurality of head chip flutes, and a head base surface facing in an axial rearward direction. The mounting protuberance exhibits rotational symmetry about the first axis, extends axially rearwardly from the head base surface, and has a plurality of circumferentially spaced apart convex clamping surfaces. The plurality of cutting portions define a cutting diameter, the plurality of head chip flutes are inscribed by an imaginary first circle having a first diameter, and the plurality of clamping surfaces are circumscribed by an imaginary second circle having a second diameter. The first diameter is greater than the second diameter, and the second diameter is less than forty percent of the cutting diameter.
1. A cutting head ( 20 , 120 ) rotatable about a first axis (A 1 ) in a first direction of rotation (R 1 ), 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);
wherein each cutting portion ( 26 ) comprises a cutting edge ( 34 ) formed at the intersection of an axially forward facing leading surface ( 32 ) and a circumferentially adjacent and rotationally forward head chip flute ( 28 ), the cutting edge ( 34 ) extending in a direction transverse to the first axis (A 1 ); and
a rigid mounting protuberance ( 24 ) devoid of resiliently displaceable elements 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 (A 1 ), 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 (A 1 ),
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 ),
in a cross-section taken in a first plane (P 1 ) perpendicular to the first axis (A 1 ) and intersecting the cap portion ( 22 ), the N head chip flutes ( 28 ) are inscribed by an imaginary first circle (C 1 ) having a first diameter (D 1 ) at N radially innermost head flute points (NH), and
in a cross-section taken in a second plane (P 2 ) perpendicular to the first axis (A 1 ) and intersecting the mounting protuberance ( 24 ), the N clamping surfaces ( 38 ) are circumscribed by an imaginary second circle (C 2 ) having a second diameter (D 2 ),
and wherein:
the first diameter (D 1 ) is greater than the second diameter (D 2 ), and
the second diameter (D 2 ) is less than forty percent of the cutting diameter (DC).
2. The cutting head ( 20 , 120 ) according to claim 1 , wherein the second diameter (D 2 ) is less than thirty percent of the cutting diameter (DC).
3. The cutting head ( 20 , 120 ) according to claim 1 , wherein:
each head flute point (NH) is contained in a radial flute plane (PF) containing the first axis (A 1 ), each radial flute plane (PF) forms a first angle (al) with a circumferentially adjacent radial clamping bisector plane (PB), and
the first angle (al) is less than thirty-five degrees.
4. The cutting head ( 20 , 120 ) according to claim 1 , wherein in the cross-section taken in the second plane (P 2 ):
the N clamping surfaces ( 38 ) form N spaced apart clamping arcs ( 42 ) coincident with the imaginary second circle (C 2 ).
5. The cutting head ( 20 , 120 ) according to claim 1 , wherein N=3.
6. The cutting head ( 20 , 120 ) according to claim 1 , wherein the mounting protuberance ( 24 ) is entirely surrounded by the head base surface ( 30 ).
7. The cutting head ( 20 , 120 ) according to claim 1 , wherein:
the mounting protuberance ( 24 ) has N joining surfaces ( 40 ) circumferentially alternating with the N clamping surfaces ( 38 ), and
each joining surface ( 40 ) intersects two circumferentially adjacent clamping surfaces ( 38 ).
8. The cutting head ( 20 , 120 ) according to claim 1 , wherein:
in a cross-section taken in a third plane (P 3 ) perpendicular to the first axis (A 1 ) and intersecting the mounting protuberance ( 24 ), the mounting protuberance ( 24 ) is circumscribed by an imaginary third circle (C 3 ) having a third diameter (D 3 ) greater than the second diameter (D 2 ), and
the second plane (P 2 ) is located between the first and third planes (P 1 , P 3 ).
9. The cutting head ( 120 ) according to claim 8 , wherein:
the third plane (P 3 ) intersects the N clamping surfaces ( 38 ), and
each clamping surface ( 38 ) is partially conical shaped.
10. The cutting head ( 20 ) according to claim 8 , wherein:
the third plane (P 3 ) does not intersect the N clamping surfaces ( 38 ), and
each clamping surface ( 38 ) is partially cylindrical shaped.
11. The cutting head ( 20 ) according to claim 8 , wherein:
the third plane (P 3 ) intersects N circumferentially spaced apart axial stopper portions ( 44 ), and
the imaginary third circle (C 3 ) circumscribes the N axial stopper portions ( 44 ).
12. The cutting head ( 20 ) according to claim 11 , wherein:
each radial clamping bisector plane (PB) intersects one of the axial stopper portions ( 44 ).
13. The cutting head ( 20 ) according to claim 11 , wherein:
each axial stopper portion ( 44 ) has a stopper surface ( 48 ) facing axially forward.
14. The cutting head ( 20 , 120 ) according to claim 1 , wherein:
a head flute depth (HD) is defined as the radial distance between the head flute points (NH) and the cutting circle (CC); and
the head flute depth (HD) is at least 60% of one-half the cutting diameter (DC).
15. The cutting head ( 20 , 120 ) according to claim 1 , wherein the N head chip flutes ( 28 ) intersect the head base surface ( 30 ).
16. The cutting head ( 20 , 120 ) according to claim 1 , wherein:
N is exactly 3;
the cap portion ( 22 ) has exactly three cutting portions ( 26 ) and exactly three head chip flutes ( 28 ) and
the mounting protuberance ( 24 ) has exactly three-fold rotational symmetry and exactly three clamping surfaces ( 38 ).
17. The cutting head ( 20 , 120 ) according to claim 1 , configured as a drill head for use in drilling operations.
18. A rotary cutting tool ( 52 , 152 ) comprising:
a tool shank ( 54 , 154 ) extending along a second axis (A 2 ) 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 (A 2 ) 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 (A 1 ) in a first direction of rotation (R 1 ), 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 (A 1 ), 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 (A 1 ),
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 (P 1 ) perpendicular to the first axis (A 1 ) and intersecting the cap portion ( 22 ), the N head chip flutes ( 28 ) are inscribed by an imaginary first circle (C 1 ) having a first diameter (D 1 ) at N radially innermost head flute points (NH), and
in a cross-section taken in a second plane (P 2 ) perpendicular to the first axis (A 1 ) and intersecting the mounting protuberance ( 24 ), the N clamping surfaces ( 38 ) are circumscribed by an imaginary second circle (C 2 ) having a second diameter (D 2 ),
and wherein:
the first diameter (D 1 ) is greater than the second diameter (D 2 ), and
the second diameter (D 2 ) 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 (A 2 ) is coincident with the first axis (A 1 ), 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 ).
19. The rotary cutting tool ( 52 , 152 ) according to claim 18 , wherein:
the N abutment portions ( 72 ) are resiliently displaceable.
20. The rotary cutting tool ( 52 , 152 ) according to claim 18 , wherein:
The N abutment portions ( 72 ) circumferentially alternate with N intermediate portions ( 76 ), and
each intermediate portion ( 76 ) has an intermediate surface ( 78 ) intersecting two circumferentially adjacent abutment surfaces ( 74 ).
21. The rotary cutting tool ( 52 ) according to claim 18 , wherein:
the clamping surface ( 38 ) is partially cylindrically shaped; and
in a cross-section taken in one of the radial clamping bisector planes (PB):
the clamping surface ( 38 ) extends parallel to the first axis (A 1 ), and
the associated abutment surface ( 74 ) is coincident therewith.
22. The rotary cutting tool ( 152 ) according to claim 18 , wherein:
the clamping surface ( 38 ) is partially conically shaped; and
in a cross-section taken in one of the radial clamping bisector planes (PB):
the clamping surface ( 38 ) diverges away from the first axis (A 1 ) as it extends axially rearwardly, and
the associated abutment surface ( 74 ) is coincident therewith.
23. The rotary cutting tool ( 52 , 152 ) according to claim 18 , wherein:
N circumferentially spaced apart shank chip flutes ( 64 ) extend from the shank's forward end ( 58 ) along the second axis (A 2 ),
in a cross-section taken in a fourth plane (P 4 ) perpendicular to the first axis (A 1 ) and intersecting the central recess ( 62 ), the N shank chip flutes ( 64 ) are inscribed by an imaginary fourth circle (C 4 ) having a fourth diameter (D 4 ) at N radially innermost shank flute points (NS), and
the fourth diameter (D 4 ) is between ninety percent and one hundred and ten percent of the first diameter (D 1 ).
24. The rotary cutting tool ( 52 , 152 ) according to claim 23 , wherein:
the N head chip flutes ( 26 ) are corresponding extensions of the N shank chip flutes ( 64 ).
25. The rotary cutting tool ( 52 , 152 ) according to claim 23 , wherein:
a tool flute depth (TD) is defined as the radial distance between the shank flute points (NS) and the cutting circle (CC); and
the tool flute depth (TD) is at least 60% of one-half the cutting diameter (DC).
26. A cutting head ( 20 , 120 ) rotatable about a first axis (A 1 ) in a first direction of rotation (R 1 ), 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 (A 1 ), 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 (A 1 ), 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 (P 1 ) perpendicular to the first axis (A 1 ) and intersecting the cap portion ( 22 ), the N head chip flutes ( 28 ) are inscribed by an imaginary first circle (C 1 ) having a first diameter (D 1 ) at N radially innermost head flute points (NH), and
in a cross-section taken in a second plane (P 2 ) perpendicular to the first axis (A 1 ) and intersecting the mounting protuberance ( 24 ), the N clamping surfaces ( 38 ) are circumscribed by an imaginary second circle (C 2 ) having a second diameter (D 2 ),
and wherein:
the first diameter (D 1 ) is greater than the second diameter (D 2 ), and
the second diameter (D 2 ) is less than forty percent of the cutting diameter (DC).
27. The cutting head ( 20 , 120 ) according to claim 26 , wherein the mounting protuberance ( 24 ) is devoid of resiliently displaceable elements.
28. The cutting head ( 20 , 120 ) according to claim 26 , wherein the cap portion ( 22 ) and the mounting protuberance ( 24 ) both exhibit N-fold rotational symmetry about the first axis (A 1 ).