INDEXABLE CUTTING INSERT

Abstract

The proposed technology relates to an indexable cutting insert (10) for a cutting tool. The cutting insert (10) comprises: a first side surface (12) and an opposing second side surface (14), and a peripheral surface (16) extending between the first side surface (12) and the second side surface (14). The cutting portion (18) comprises a first cutting face (24) and an opposing second cutting face (26), a flank face (28) extending between the first cutting face (24) and the second cutting face (26), a first cutting edge (20) between the first cutting face (24) and the flank face (28), and a second cutting edge (22) between the second cutting face (26) and the flank face (28). The cutting portion (18) is bisected by a first plane (AA′) transverse to the first side surface (12) and the cutting portion (18) has a biconcave cross-section transverse to the first plane (AA′).

Claims

1-17. (canceled)

18. An indexable cutting insert for a cutting tool, comprising: a first side surface, an opposing second side surface, and a peripheral surface extending between the first side surface and the second side surface; and a cutting portion comprising a first cutting face, an opposing second cutting face, a flank face extending between the first cutting face and the second cutting face, a first cutting edge between the first cutting face and the flank face, and a second cutting edge between the second cutting face and the flank face; wherein the cutting portion is bisected by a first plane transverse to the first side surface; and wherein the cutting portion has a cross-section transverse to the first plane that is concave on both the first side surface and on the second side surface.

19. The cutting insert according to claim 18, wherein, on the cutting portion, the first side surface is concave and defines a portion of a surface of a first elliptical cylinder having a first cylinder axis in the first plane; and wherein, on the cutting portion, the second side surface is concave and defines a portion of a surface of a second elliptical cylinder having a second cylinder axis in the first plane.

20. The cutting insert according to claim 19, wherein the first cylinder axis and the second cylinder axis diverge in the direction of the flank face.

21. The cutting insert according to claim 19, wherein each of the first cylinder and the second cylinder has a transverse cross-section that forms an ellipse, wherein the transverse cross-section has a semi-major axis that is transverse to the first plane.

22. The cutting insert according to claim 18, wherein the cutting portion has a width between the first side surface and the second side surface that increases towards the flank face.

23. The cutting insert according to claim 18, wherein the cutting portion is bisected by a second plane transverse to the first plane and centered between and extending in the same directions as the first side surface and the second side surface, and wherein the cutting portion has a radial side clearance angle in the range 1° to 2.5° between the second plane and a line tangential to the first side surface at the first cutting edge and at the second cutting edge and in a plane parallel to the first plane.

24. The cutting insert according to claim 23, wherein the cutting portion has a tangential side clearance angle in the range 2.5° to 10° between the second plane and a line tangential to the first side surface at one of the first cutting edge and the second cutting edge, and in a plane perpendicular to the first plane and the second plane.

25. The cutting insert (10) according to claim 18, wherein the first cutting face has a first rake portion at the first cutting edge, and the second cutting face has a second rake portion at the second cutting edge, wherein the first rake portion and the second rake portion curve inward with respect to the cutting portion.

26. The cutting insert according to claim 18, wherein the cutting insert has a base portion, the cutting portion has a proximal end and a distal end, the cutting portion is attached to the base portion at the proximal end of the cutting portion, the first cutting edge and the second cutting edge are located at the distal end of the cutting portion, and the base portion has a rounded profile at the proximal end of the base portion.

27. The cutting insert according to claim 26, wherein the base portion has a through-going hole between the first side surface and the second side surface.

28. The cutting insert according to claim 26, wherein the base portion has a portion shaped as a sector of a ring with a sector angle in the range 60° to 180°.

29. The cutting insert according to claim 28, wherein the portion shaped as a sector of a ring has a uniform radial thickness.

30. The cutting insert according to claim 26, wherein the cutting insert has a thickness transverse to the first plane first plane that increases when going from the proximal end of the base portion to the distal end of the cutting portion.

31. The cutting insert according to claim 18, wherein the cutting insert constitutes a unitary body.

32. The cutting insert according to claim 18, wherein the cutting insert is of sintered or cemented carbide.

33. A cutting tool assembly for machining a work part rotating on a rotational axis, comprising: a cutting tool; and an indexable cutting insert supported by the cutting tool, the indexable cutting insert comprising: a first side surface, an opposing second side surface, and a peripheral surface extending between the first side surface and the second side surface; and a cutting portion comprising a first cutting face, an opposing second cutting face, a flank face extending between the first cutting face and the second cutting face, a first cutting edge between the first cutting face and the flank face, and a second cutting edge between the second cutting face and the flank face; wherein the cutting portion is bisected by a first plane transverse to the first side surface; and wherein the cutting portion has a cross-section transverse to the first plane that is concave on both the first side surface and on the second side surface; wherein the cutting tool is further configured to support the indexable cutting insert so as to orient the indexable cutting insert with the first plane transverse to the rotational axis.

34. A method for machining a work part rotating on a rotational axis, the method comprising the steps of: (a) providing an indexable cutting insert, comprising: a first side surface, an opposing second side surface, and a peripheral surface extending between the first side surface and the second side surface; and a cutting portion comprising a first cutting face, an opposing second cutting face, a flank face extending between the first cutting face and the second cutting face, a first cutting edge between the first cutting face and the flank face, and a second cutting edge between the second cutting face and the flank face; wherein the cutting portion is bisected by a first plane transverse to the first side surface; and wherein the cutting portion has a cross-section transverse to the first plane that is concave on both the first side surface and on the second side surface; and (b) supporting the indexable cutting insert in a cutting tool so that the indexable cutting insert is oriented with the first plane transverse to the rotational axis of the rotating work part.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0050] A more complete understanding of the abovementioned and other features and advantages of the proposed technology will be apparent from the following detailed description of a preferred embodiment in conjunction with the appended drawings, wherein:

[0051] FIG. 1 is perspective view of an embodiment of a cutting insert,

[0052] FIG. 2 is a top view of the cutting insert of FIG. 1,

[0053] FIG. 3 is a side view of the cutting insert of FIG. 1, and

[0054] FIG. 4 is a front view of the cutting insert of FIG. 1.

DESCRIPTION OF THE DRAWINGS

[0055] FIGS. 1-4 show different views of an embodiment of cutting insert 10 according to the proposed technology. The cutting insert 10 is intended for turning applications. The cutting insert 10 constitutes a unitary body of sintered tungsten carbide. The cutting insert 10 has a first side surface 12 and an opposing second side surface 14, and a peripheral surface 16 extending between the first side surface 12 and the second side surface 14. The first side surface 12 and the second side surface 14 extend along the complete length of the cutting insert 10, and the peripheral surface 16 encircles the complete cutting insert 10. The cutting insert is divided into a single cutting portion 18 and a single base portion 38. The cutting portion has been shaped by grinding, while the base portion 38 has been shaped in the sintering process.

[0056] The cutting portion 18 has a proximal end 34 and a distal end 36. The cutting portion 18 is attached to the base portion 38 at the proximal end 34 of the cutting portion 18. Similarly, the base portion 38 has a proximal end 52 and a distal end 54. The base portion 38 is attached to the cutting portion 18 at the distal end 54 of the base portion 38.

[0057] The cutting portion 18 and the base portion 38 are bisected by a first plane AA′ transverse to the first side surface 12. This means that the first plane AA′ divides each of the cutting portion 18 and the base portion 38 in two congruent portions, or the complete cutting insert 10 in two congruent portions. The cut of first plane AA′ is indicated by the dashed lines AA′ in FIGS. 2 and 4. The congruent portions have a 180° reflection and rotation symmetry with respect to the first plane AA′, as is apparent from FIGS. 1-4. Similarly, the cutting portion 18 and the base portion 38 are bisected by a second plane BB′ transverse to the first plane AA′, which means that the second plane BB′ is roughly aligned with the first side surface 12 and the second side surface 14. The second plane BB′ divides each of the cutting portion 18 and the base portion 38 in two congruent portions, or the complete cutting insert 10 in two congruent portions. The cut of second plane BB′ is indicated by the dashed lines BB′ in FIGS. 3 and 4. The congruent portions also have a 80° reflection and rotation symmetry with respect to the second plane BB″, as is apparent from FIGS. 1-4.

[0058] The cutting portion 18 has a first cutting face 24 and an opposing second cutting face 26. A flank face 28 extends between the first cutting face 24 and the second cutting face 24. It further has a first cutting edge 20 between the first cutting face 24 and the flank face 28 and a second cutting edge 22 between the second cutting face 26 and the flank face 28. The first cutting edge 20, the second cutting edge 22, and the flank face 28 are located at the distal end 36 of the cutting portion 18. The cutting edges 20 and 22 are parallel and extend from the first side surface 12 to the second side surface 14. They define the same cutting width, since the first plane AA′ and the second plane divide the cutting portion in congruent portions.

[0059] The base portion 38 has a first planar portion 48 on the first side surface 12 and a second planar portion 50 on the second side surface 14. The first planar portion and the second planar portion are parallel. A through-going circular hole 42 extends between the first planar portion 48 and the second planar portion 50.

[0060] The first side surface 12 of the cutting portion 18 is concave and has the shape of a portion of a surface of a first cylinder having its axis in the first plane AA′. Similarly, the second side surface 14 of the cutting portion 18 is concave has the shape of a portion of a surface of a second cylinder also having its axis in the first plane AA′. The axis of the first cylinder and the axis of the second cylinder diverge in the direction from the proximal end 34 to the distal end 36 of the cutting portion 38, or towards the flank face 28, and both define an angle to the second plane BB′ of 2°. The first cylinder and the second cylinder are congruent elliptic cylinders. A portion of a cross-section of en elliptic cylinder is indicated by the dashed line DD′. The portion of the surface of the first cylinder and the portion of the surface of the second cylinder are congruent.

[0061] The fact that the axes of the elliptic cylinders diverge in the direction of the flank face 28 means that the cutting portion 18 has a width between the first side surface 12 and the second side surface 14 that increases towards the flank face 28, and that the first side surface 12 and the second side surface 14 diverge from one another when going from the proximal end 34 to the distal end 36 of the cutting portion 18. The fact that both axes of the elliptic cylinders define an angle to the second plane BB′ of 2° means that the cutting portion 18 has a radial side clearance angle 64 of 2° on either side of the cutting portion 18.

[0062] The fact that both the first side surface 12 and the second side surface 14 are concave, and the fact that the elliptic cylinders are oriented in the same general directions, means that cutting portion 18 has a biconcave cross-section transverse to the first plane AA′ along the complete length from the proximal end 34 to the flank face 28. Effectively, this means that the cutting portion 18 has a cross-section transverse to the first plane AA′ that is concave on the first side surface 12 and on the second side surface 14. The biconcave cross-section causes the cutting portion 18 to have a tangential side clearance angle 66 of 4°.

[0063] The flank face 28 is concave and curves inwards with respect to the cutting portions 18. This causes the cutting portion 18 to have a front clearance during use, both with respect to the first cutting edge 20 and the second cutting edge 22.

[0064] The first cutting face 24 has a first rake portion 56 at the first cutting edge 20. Similarly, the second cutting face 24 has a second rake portion 58 at the second cutting edge 22. Both rake portions 56 and 58 are concave and curve inward with respect to the cutting portion 18 and define a positive rake angle with respect to a work part in the intended orientation during use.

[0065] The first cutting face 24 has a first planar face portion 68 extending from the proximal end 34 of the cutting portion 18 to the first rake portion 56. Similarly, the second cutting face 26 has a second planar face portion 70 extending from the proximal end 34 of the cutting portion 18 to the second rake portion 58. The first planar face portion 68 and the second planar face portion 70 diverge from one another when going from the proximal end 34 towards the distal end 36 of the cutting portion 18. This means that the cutting portion 18 has a thickness, or height, transverse to the first plane AA′ that increases when going from the proximal end 34 to the distal end 36 of the cutting portion 18, disregarding the first and second rake portions 56 and 58. The first planar face portion 68 and the second planar face portion 70 define an angle between them of 12°. The maximum height of the cutting insert 10 is defined by the distance between the first cutting edge 20 and the second cutting edge 22. The maximum height is about eight times greater than the cutting width corresponding to the length of the first cutting edge 20 and the second cutting edge 22. The base portion 38 is intended to be attached to a tool holder by a screw received in the through-going circular hole 42 and operatively connecting to a threaded bore in the tool holder. Each of the first planar portion 48 and the second planar portion 50 of the base portion 38 is intended to, one at a time, press against a planar surface on a tool holder during use.

[0066] The axis DD′ of the circular hole 42 is in the first plane AA′ and perpendicular to the second plane BB′. The base portion 38 has a first beveled edge 44 between the circular hole 42 and the first side surface 12 and a second beveled edge 46 between the circular hole 42 and the second side surface 14.

[0067] The base portion 38 has a rounded profile at its proximal end 52 with a portion 60 shaped as a sector of a ring of uniform radial thickness and located at the proximal end 52.

[0068] This means that a portion 62 of the peripheral surface 16 on the base portion 38 is convex in the second plane BB′ and has the shape of a portion of a surface of a third cylinder with an axis that is collinear or coaxial with the axis DD′ of the circular hole 42. It also means that the third cylinder and the circular hole 42 are concentric.

[0069] The peripheral surface 16 is a smooth surface on the base portion 38 without any sharp features. The peripheral surface 16 is curved only in the second plane BB′ around the base portion, which means that it is curved in a single dimension only. The peripheral surface has the same profile in a cross-section aligned or parallel with the second surface BB′.

[0070] There is no bevel between the first side surface 12 and the peripheral surface 16 or between second side surface 14 and the peripheral surface 16. The first side surface 12 and the peripheral surface 16 define right angle between them where they connect. Similarly, the second side surface 14 and the peripheral surface 16 define right angle between them where they connect. This means that at each point on the base portion 38 between the first side surface 12 and the peripheral surface 16, the first side surface 12 is at a right angle to the peripheral surface 16, and that at each point on the base portion 38 between the second side surface 14 and the peripheral surface 16, the second side surface 14 is at a right angle to the peripheral surface 16.

ITEM LIST

[0071] AA′ first plane [0072] BB′ second plane of first cylinder [0073] CC′ axis of circular hole [0074] 10 insert [0075] 12 first side surface [0076] 14 second side surface [0077] 16 peripheral surface [0078] 18 cutting portion [0079] 20 first cutting edge [0080] 22 second cutting edge [0081] 24 first cutting face [0082] 26 second cutting face [0083] 28 flank face [0084] 32 bisection [0085] 34 proximal end of cutting portion [0086] 36 distal end of cutting portion [0087] 38 base portion [0088] 42 circular hole [0089] 44 first beveled edge [0090] 46 second beveled edge [0091] 48 first planar portion [0092] 50 second planar portion [0093] 52 proximal end of base portion [0094] 54 distal end of base portion [0095] 56 first rake portion [0096] 58 second rake portion [0097] 60 ring-shaped portion [0098] 62 convex portion of peripheral surface [0099] 64 radial side clearance angle [0100] 66 tangential side clearance angle [0101] 68 first planar face [0102] 70 second planar face