Tool shank with head support surface having central recess provided with resiliently displaceable abutment portions
A tool shank has a head receiving pocket at a forward end, and a plurality of chip flutes extending rearwardly therefrom along a longitudinal axis. The head receiving pocket has a support surface transverse to the longitudinal axis. A central recess is formed in the support surface and extends rearwardly therefrom. The central recess has a plurality of resiliently displaceable abutment portions circumferentially alternating with and spaced apart by a plurality of intermediate portions. Each abutment portion has a radially inward facing abutment surface, and each intermediate portion has an intermediate surface intersecting two circumferentially adjacent abutment surfaces. A rotary cutting tool includes the shank and a cutting head releasably mounted thereto. The cutting head has a mounting portion provided with a base surface and an engagement member protruding therefrom. In an assembled position, the engagement member is resiliently retained in the central recess against the plurality of abutment surfaces.
1. A tool shank ( 20 ) having a longitudinal axis of rotation (A 1 ) establishing a forward-to-rearward direction (D F , D R ) and comprising:
a head receiving pocket ( 22 ) at a forward end ( 24 ), and a plurality of chip flutes ( 26 ) extending in the rearward direction (DR) therefrom along the longitudinal axis of rotation (A 1 ),
the head receiving pocket ( 22 ) having a support surface ( 30 ) transverse to the longitudinal axis of rotation (A 1 ), and a central recess ( 32 ),
wherein:
the central recess ( 32 ) is circumferentially confined and formed in the support surface ( 30 ) and extends in the rearward direction (DR) therefrom, along the longitudinal axis of rotation (A 1 ),
the central recess ( 32 ) has a plurality of resiliently displaceable abutment portions ( 38 ) circumferentially alternating with and spaced apart by a plurality of intermediate portions ( 40 ),
each abutment portion ( 38 ) has a radially inward facing abutment surface ( 42 ), and
each intermediate portion ( 40 ) has an intermediate surface ( 44 ) intersecting two circumferentially adjacent abutment surfaces ( 42 ).
2. The tool shank ( 20 ) according to claim 1 , wherein
in a cross-section taken in a first plane (P 1 ) perpendicular to the longitudinal axis of rotation (A 1 ) and passing through the central recess ( 32 ):
each abutment surface ( 42 ) has a first circumferential angular extent (E 1 ),
each intermediate surface ( 44 ) has a second circumferential angular extent (E 2 ), and
the combined circumferential angular extent of the plurality of abutment surfaces ( 42 ) and the plurality of intermediate surfaces ( 44 ) is equal to 360°.
3. The tool shank ( 20 ) according to claim 2 , wherein:
the second circumferential angular extent (E 2 ) is greater than the first circumferential angular extent (E 1 ).
4. The tool shank ( 20 ) according to claim 1 , wherein:
in a cross-section taken in a first plane (P 1 ) perpendicular to the longitudinal axis of rotation (A 1 ) and passing through the central recess ( 32 ):
an imaginary first circle (C 1 ) coaxial with the longitudinal axis of rotation (A 1 ) inscribes the central recess ( 32 ).
5. The tool shank ( 20 ) according to claim 4 , wherein:
in the absence of radially outward forces (FO) being applied to the plurality of abutment surfaces ( 42 ), the imaginary first circle (C 1 ) has a first diameter (D 1 ),
in the presence of radially outward forces (FO) being applied to the plurality of abutment surfaces ( 42 ), the imaginary first circle (C 1 ) has a first loaded diameter (DL 1 ), and
the first diameter (D 1 ) is less than the first loaded diameter (DL 1 ).
6. The tool shank ( 20 ) according to claim 4 , wherein
in the cross-section taken in the first plane (P 1 ):
an imaginary second circle (C 2 ) coaxial with the longitudinal axis of rotation (A 1 ) is tangent to the plurality of chip flutes ( 26 ) at a plurality of first flute points (NF 1 ), and
a third plane (P 3 ) containing the longitudinal axis of rotation (A 1 ) and at least one of the first flute points (NF 1 ) intersects at least one of the abutment surfaces ( 42 ).
7. The tool shank ( 20 ) according to claim 6 , wherein:
the imaginary first circle (C 1 ) has a first diameter (D 1 ),
the imaginary second circle (C 2 ) has a second diameter (D 2 ), and
first diameter (D 1 ) is greater than half the second diameter (D 2 ).
8. The tool shank ( 20 ) according to claim 6 , wherein:
a radial axis (A 2 ) is formed at the intersection of the first and third planes (P 1 , P 3 ), and
each first flute point (NF 1 ) is located a minimum first distance (d 1 ) from its adjacent abutment surface ( 42 ) along the radial axis (A 2 ).
9. The tool shank ( 22 ) according to claim 8 , wherein
in the cross-section taken in the first plane (P 1 ):
each chip flute ( 26 ) has a second flute point (NF 2 ) spaced apart from the first flute point (NF 1 ),
the second flute point (NF 2 ) is located a minimum second distance (d 2 ) from its adjacent intermediate surface ( 44 ), and
the minimum second distance (d 2 ) is equal to or less than the minimum first distance (d 1 ).
10. The tool shank ( 20 ) according to claim 4 , wherein:
the imaginary first circle (C 1 ) contacts the plurality of abutment surfaces ( 42 ).
11. The tool shank ( 20 ) according to claim 1 , wherein:
the plurality of intermediate surfaces ( 44 ) extend to a first recess depth (H 1 ) rearward of the support surface ( 30 ) to a central recess floor ( 45 );
the plurality of abutment surfaces ( 42 ) extend to a second recess depth (H 2 ) rearward of the support surface ( 30 ) and are longitudinally spaced apart from the central recess floor ( 45 ); and
a ratio of the first recess depth (H 1 ) to the second recess depth (H 2 ) is between 1.3 and 2.5 (1.3<H1/H2<2.5).
12. The tool shank ( 20 ) according to claim 1 , wherein:
in a cross-section taken in a first plane (P 1 ) perpendicular to the longitudinal axis of rotation (A 1 ) and passing through the central recess ( 32 ), the central recess ( 32 ) does not intersect any of the plurality of chip flutes ( 26 ).
13. The tool shank ( 20 ) according to claim 1 , wherein:
the plurality of abutment surfaces ( 42 ) diverge from one another in the rearward direction (DR).
14. The tool shank ( 20 ) according to claim 1 , wherein:
the plurality of intermediate surfaces ( 44 ) intersect the support surface ( 30 ).
15. The tool shank ( 20 ) according to claim 1 , wherein:
the plurality of abutment portions ( 38 ) are resiliently displaceable in a radially outward direction (DO).
16. The tool shank ( 20 ) according to claim 1 , wherein:
in a tool shank side view tangential to the support surface ( 30 ), the entire central recess ( 32 ) is hidden from view, with no portion of the abutment surfaces ( 42 ) and the intermediate surfaces ( 44 ) being visible.
17. A rotary cutting tool ( 52 ) comprising the tool shank ( 20 ) in accordance with claim 1 , and a cutting head ( 54 ) releasably mounted in the head receiving pocket ( 22 ),
the cutting head ( 54 ) comprising:
a cutting portion ( 56 ) and a mounting portion ( 58 ),
the mounting portion ( 58 ) having a base surface ( 60 ) and an engagement member ( 62 ) protruding therefrom along a head axis (A 3 ),
wherein in an assembled position:
the base surface ( 60 ) faces the support surface ( 30 ),
the head axis (A 3 ) is coincident with the longitudinal axis of rotation (A 1 ), and
the engagement member ( 62 ) is resiliently retained in the central recess ( 32 ) against the plurality of abutment surfaces ( 42 ).
18. The rotary cutting tool ( 52 ) according to claim 17 , wherein
in a cross-section taken in a first plane (P 1 ) perpendicular to the longitudinal axis of rotation (A 1 ) and passing through the central recess ( 32 ):
an imaginary first circle (C 1 ) coaxial with the longitudinal axis of rotation (A 1 ) inscribes the central recess ( 32 ), and
wherein:
in a non-assembled position, in which the engagement member ( 62 ) is not resiliently retained in the central recess ( 32 ), the imaginary first circle (C 1 ) has a first diameter (D 1 ),
in the assembled position, the imaginary first circle (C 1 ) has a first assembly diameter (DA 1 ), and
the first diameter (D 1 ) is less than the first assembly diameter (DA 1 ).
19. The rotary cutting tool ( 52 ) according to claim 18 , wherein:
the imaginary first circle (C 1 ) contacts the plurality of abutment surfaces ( 42 ).
20. The rotary cutting tool ( 52 ) according to claim 17 , wherein:
the engagement member ( 62 ) has a plurality of radially outward facing engagement surfaces ( 64 ) circumferentially alternating with a plurality of joining surfaces ( 66 ), and
the plurality of engagement surfaces ( 64 ) make contact with the plurality of abutment surfaces ( 42 ).
21. The rotary cutting tool ( 52 ) according to claim 20 , wherein:
in a cross-section taken in a first plane (P 1 ) perpendicular to the longitudinal axis of rotation (A 1 ) and passing through the central recess ( 32 ):
an imaginary third circle (C 3 ) coaxial with the longitudinal axis of rotation (A 1 ) circumscribes the engagement member ( 62 ).
22. The rotary cutting tool ( 52 ) according to claim 21 , wherein:
the imaginary third circle (C 3 ) contacts the plurality of engagement surfaces ( 64 ).
23. The rotary cutting tool ( 52 ) according to claim 21 , wherein:
the plurality of engagement surfaces ( 64 ) form a plurality of spaced apart engagement arcs ( 68 ) coincident with the imaginary third circle (C 3 ).
24. The rotary cutting tool ( 52 ) according to claim 20 , wherein:
the plurality of engagement surfaces ( 64 ) diverge from one another in the rearward direction (DR).
25. The rotary cutting tool ( 52 ) according to claim 17 , wherein:
the base surface ( 60 ) makes contact with the support surface ( 30 ), or a plurality of shoulder surfaces ( 63 ) offset therefrom.
26. A method of assembling the rotary cutting tool ( 52 ) according to claim 17 , in which the engagement member ( 62 ) has a plurality of radially outward facing engagement surfaces ( 64 ) circumferentially alternating with a plurality of joining surfaces ( 66 ), the method comprising the steps of:
orienting the base surface ( 60 ) to face the support surface ( 30 );
aligning the head axis (A 3 ) with the longitudinal axis of rotation (A 1 );
rotationally aligning the plurality of engagement surfaces ( 64 ) with the plurality of intermediate surfaces ( 44 );
inserting the engagement member ( 62 ) into the central recess ( 32 ); and
rotating the cutting head ( 54 ) about its head axis (A 3 ) until the plurality of engagement surfaces ( 64 ) are resiliently retained against the plurality of abutment surfaces ( 42 ).
27. The method according to claim 26 , wherein:
in step d), the engagement member ( 62 ) is inserted into the central recess ( 32 ) until the base surface ( 60 ) makes contact with the support surface ( 30 ), or a plurality of shoulder surfaces ( 63 ) offset therefrom.
28. The method according to claim 27 , wherein:
a plurality of drive members ( 34 ) protrude forwardly from the support surface ( 30 ), each drive member ( 34 ) including a drive surface ( 36 ) facing in a rotation direction (R) about the longitudinal axis of rotation (A 1 ),
the mounting portion ( 58 ) has a plurality of circumferentially spaced apart side surfaces ( 70 ) extending away from the base surface ( 60 ) towards the cutting portion ( 56 ), each side surface ( 70 ) including a torque transmission surface ( 72 ), and
in step e), the cutting head ( 54 ) is rotated about its head axis (A 3 ) in a direction opposite to the rotation direction (R) until each drive surface ( 36 ) makes contact with one of the torque transmission surfaces ( 72 ).