Circular cutting insert having non-circular peripheral edge
A cutting tool has an insert holder with an indexable cutting insert removably secured therein. The cutting insert has upper and lower end surfaces with a peripheral side surface and a through bore extending therebetween, and a plurality of upper cutting edges formed on an upper peripheral edge. The peripheral side surface includes a non-circular upper relief surface adjacent the upper peripheral edge and a circular upper abutment surface spaced apart from the upper peripheral edge. Each upper cutting edge exhibits mirror symmetry about a bisector plane, and is non-linear in a side view. The through bore has an inner undercut formed by upper and lower bore surfaces located on opposite sides of a median plane, and a clamping member makes contact with one of the upper and lower bore surfaces at an inner contact zone located between the median plane and a seat surface of the insert holder.
1. An indexable cutting insert ( 20 , 120 ) comprising:
opposing upper and lower end surfaces ( 22 , 24 ) with a continuous peripheral side surface ( 26 ) and a central axis (A 1 ) extending therebetween,
upper and lower peripheral edges ( 28 , 30 ) formed at the intersection of the peripheral side surface ( 26 ) and the upper and lower end surfaces ( 22 , 24 ), respectively, and
a number N upper cutting edges ( 36 ) formed on the upper peripheral edge ( 28 ) where N≥2,
the peripheral side surface ( 26 ) including:
adjacent to the upper peripheral edge ( 28 ), a continuous upper relief surface ( 32 ) which is non-circular in a cross-section taken in a first horizontal plane (P H 1 ) perpendicular to the central axis (A 1 ), and
spaced apart from the upper peripheral edge ( 28 ), a continuous upper abutment surface ( 34 a ) which is circular in a cross-section taken in a second horizontal plane (P H 2 ) perpendicular to the central axis (A 1 ),
wherein:
each upper cutting edge ( 36 ) exhibits mirror symmetry about a bisector plane (P B ) containing the central axis (A 1 ) and bisecting said each upper cutting edge ( 36 );
in an end view of the cutting insert ( 20 , 120 ), the upper peripheral edge ( 28 ) is non-circular and exhibits N-fold rotational symmetry about the central axis (A 1 ); and
in a side view of the cutting insert ( 20 , 120 ), each upper cutting edge ( 36 ) is non-linear.
2. The cutting insert ( 20 , 120 ) according to claim 1 , wherein each upper cutting edge ( 36 ) circumferentially extends 360/N° along the upper peripheral edge ( 28 ).
3. The cutting insert ( 20 , 120 ) according to claim 1 , wherein the upper abutment surface ( 34 a ) is conical, having an upper abutment diameter (Du) which decreases in a direction away from the upper end surface ( 22 ).
4. The cutting insert ( 20 , 120 ) according to claim 1 , wherein any point on the upper peripheral edge ( 28 ) is located further from the central axis (A 1 ) than any point on the upper abutment surface ( 34 a ).
5. The cutting insert ( 20 , 120 ) according to claim 1 , wherein:
the cutting insert ( 20 , 120 ) exhibits mirror symmetry about a median plane (M) perpendicular to the central axis (A 1 ), and
the upper relief and upper abutment surfaces ( 32 , 34 a ) are located between the upper end surface ( 22 ) and the median plane (M).
6. The cutting insert ( 20 , 120 ) according to claim 1 , wherein in an end view of the cutting insert ( 20 , 120 ), each upper cutting edge ( 36 ) is non-linear.
7. The cutting insert ( 20 , 120 ) according to claim 1 , wherein in an end view of the cutting insert ( 20 , 120 ), each upper cutting edge ( 36 ) is outwardly convex in relation to the central axis (A 1 ).
8. The cutting insert ( 20 , 120 ) according to claim 1 , wherein:
the peripheral side surface ( 26 ) includes a continuous lower relief surface ( 50 ) adjacent the lower peripheral edge ( 30 ) and a continuous lower abutment surface ( 34 b ) spaced apart from the lower peripheral edge ( 30 ); and
the lower relief surface ( 50 ) is identical to the upper relief surface ( 32 ); and
the lower abutment surface ( 34 b ) is identical to upper abutment surface ( 34 a ).
9. The cutting insert ( 20 , 120 ) according to claim 8 , wherein in cross-sections taken in mutually perpendicular first and second vertical planes (P v 1 , P V 2 ) containing the central axis (A 1 ) and intersecting the peripheral side surface ( 26 ), the upper and lower abutment surfaces ( 34 a , 34 b ) together form a V-shape.
10. The cutting insert ( 20 , 120 ) according to claim 9 , wherein in the cross-sections taken in the first and second vertical planes (P V 1 , P V 2 ), the upper and lower abutment surfaces ( 34 a , 34 b ) together form an external obtuse abutment angle (α 2 ).
11. The cutting insert ( 20 , 120 ) according to claim 8 , wherein in a cross-section taken in any plane containing the central axis (A 1 ), the upper and lower abutment surfaces ( 34 a , 34 b ) form a V-shape.
12. The cutting insert ( 20 , 120 ) according to claim 1 , wherein in an end view of the cutting insert ( 20 , 120 ), a first imaginary circle (C 1 ) circumscribes the upper peripheral edge ( 28 ) at N discrete radially outermost points (No 1 , No 2 , No 3 , No 4 ).
13. The cutting insert ( 20 , 120 ) according to claim 12 , wherein each upper cutting edge ( 36 ) extends between two of the N radially outermost points (No 1 , No 2 , No 3 , No 4 ).
14. The cutting insert ( 20 , 120 ) according to claim 12 , wherein any two circumferentially adjacent upper cutting edges ( 36 ) merge at one of the N radially outermost points (No 1 , No 2 , No 3 , No 4 ).
15. The cutting insert ( 20 ) according to claim 12 , wherein the N radially outermost points (No 1 , No 2 , No 3 , No 4 ) are located closer to the second horizontal plane (P H 2 ) than any other point on the upper peripheral edge ( 28 ).
16. The cutting insert ( 120 ) according to claim 1 , wherein each upper cutting edge ( 36 ) has a plurality of discrete axially uppermost points (Nu 1 , Nu 2 , Nu 3 , Nu 4 ).
17. The cutting insert ( 20 , 120 ) according to claim 1 , wherein the upper peripheral edge ( 28 ) has exactly four upper cutting edges ( 36 ), and N=4.
18. The cutting insert ( 20 , 120 ) according to claim 1 , wherein:
the upper end surface ( 22 ) includes a planar upper support surface ( 38 ), and
the upper peripheral edge ( 28 ) is entirely located closer to the second horizontal plane (P H 2 ) than the upper support surface ( 38 ).
19. The cutting insert ( 20 , 120 ) according to claim 18 , comprising a through bore ( 40 ) coaxial with the central axis (A 1 ) opening out to the upper support surface ( 38 ).
20. The cutting insert ( 20 , 120 ) according to claim 18 , wherein:
the upper end surface ( 22 ) includes a continuous rake surface ( 42 ) adjacent to the upper peripheral edge ( 28 ) and a ramp surface ( 44 ) adjacent to the upper support surface ( 38 );
the rake surface ( 42 ) extends radially inwardly towards the second horizontal plane (P H 2 ); and
the ramp surface ( 44 ) extends radially outwardly towards the second horizontal plane (P H 2 ).
21. The cutting insert ( 20 , 120 ) according to claim 18 , wherein the ramp surface ( 44 ) is interrupted by a plurality of circumferentially spaced apart protrusions ( 46 ).
22. The cutting insert ( 20 , 120 ) according to claim 18 , wherein each of the protrusions ( 46 ) is partially located on the rake surface ( 42 ).
23. The cutting insert ( 20 , 120 ) according to claim 21 , wherein, in an end view of the cutting insert ( 20 , 120 ), each of the protrusions ( 46 ) includes a convex shaped radially outer portion ( 48 ).
24. The cutting insert ( 20 , 120 ) according to claim 21 , wherein the plurality of protrusions ( 46 ) are greater in number than the plurality of N upper cutting edges ( 36 ).
25. The cutting insert ( 20 , 120 ) according to claim 21 , wherein the plurality of protrusions ( 46 ) are greater in number, by at least a factor of six, than the plurality of N upper cutting edges ( 36 ).