Cutting insert having linear cutting edge portion and concave cutting edge portion

Abstract

A cutting insert having a linear cutting edge portion and a concave cutting edge portion includes a top surface, a bottom surface, and a plurality of sidewalls extending between the top surface and the bottom surface. A central axis of the cutting insert extends through the top surface and the bottom surface. A peripheral cutting edge is defined at an interface of each sidewall and the top surface. Each cutting edge includes a linear cutting edge portion having an end connected to a concave cutting edge portion, the concave cutting edge portion being curved inwardly in a plane perpendicular to a first plane containing the central axis, wherein at least one linear cutting edge portion and its corresponding end are parallel to the first plane containing the central axis.

Description

[0001] This application is a divisional application of an invention patent application with an application date of October 9, 2015, application number 201510648942.5, and invention name “Cutting insert with linear cutting edge portion and concave cutting edge portion”.

[0002] Cross-references to related patent applications

[0003] This application claims the benefit of U.S. Patent Application No. 14 / 190,454, filed on February 26, 2014, which is hereby incorporated by reference in its entirety and claims the benefit of Indian Application No. 1249 / CHE / 2013, filed on March 22, 2013, which is hereby incorporated by reference in its entirety. Technical Field

[0004] The present invention generally relates to a cutting insert to be used in a cutting tool during a machining operation. More particularly, the present invention relates to a cutting insert having a linear cutting edge portion and a concave cutting edge portion. Background Art

[0005] Cutting inserts of various geometries used with various types of cutting tools during machining operations are well known. One example is various types of drills for drilling or boring cylindrical holes in metal workpieces. The cutting or boring action of the drill can be performed by an elongated, substantially cylindrical drill that is typically attached to a tool holder / drive device at one end and contains one or more cutting inserts for engaging the workpiece at the opposite end. The use of replaceable cutting inserts is well known and allows for quick replacement of the inserts when the cutting surface of the cutting insert wears, as well as allowing one drill to be used for a variety of different drilling or boring applications by simply replacing the insert rather than the entire drill assembly. In addition, indexable cutting inserts are typically used so that multiple sides of the cutting insert can be used for cutting to extend the useful life of the cutting insert.

[0006] Once the cutting insert engages the workpiece, a large number of forces act on or are applied to the cutting insert. These forces, in turn, directly affect the nature and quality of the cutting operation, that is, the nature and quality of the cutting, drilling or boring action on the workpiece.

[0007] The manufacture and installation / replacement of cutting inserts can be expensive and time consuming. It is therefore important that the cutting inserts are durable and wear resistant while still being able to effectively provide the required cutting operation.

[0008] Therefore, there is a continuing need for improved cutting inserts that overcome the shortcomings, limitations and deficiencies of known cutting inserts. For example, there is a continuing need for improved cutting inserts that can effectively absorb cutting forces and reduce / minimize the amount of forces acting on the cutting insert during a cutting operation. For another example, there is a continuing need for improved cutting inserts with improved durability and wear resistance. Summary of the invention

[0009] According to one aspect of the present invention, a cutting blade includes a top surface, a bottom surface, and a plurality of side walls extending between the top surface and the bottom surface. The central axis of the cutting blade extends through the top surface and the bottom surface. A peripheral cutting edge is defined at the junction of each side wall and the top surface. Each cutting edge includes a linear cutting edge portion and a concave cutting edge portion, and the concave cutting edge portion is bent inward in a plane perpendicular to the plane containing the central axis. A rounded corner portion connects two adjacent cutting edges. Each linear cutting edge portion extends from a rounded corner portion to a concave cutting edge portion, and each concave cutting edge portion extends from the linear cutting edge portion to another rounded corner portion.

[0010] According to another aspect of the present invention, a cutting insert includes an indexable polygonal insert body having a top surface, an opposing bottom seating surface, and a plurality of side walls extending between the top surface and the bottom seating surface. The cutting insert also includes a peripheral cutting edge defined at the intersection of each side wall and the top surface, each cutting edge including a linear cutting edge portion and a concave cutting edge portion having a greater length than the linear cutting edge portion. The concave cutting edge portion is bent inwardly in a plane perpendicular to a plane containing a central axis of the cutting insert, the central axis extending through the top surface and the bottom seating surface. The insert body also includes a radiused corner portion connecting two adjacent cutting edges.

[0011] According to another aspect of the present invention, a drill tool includes a tool body, the tool body including an axially rearward end portion having a shank portion and an axially forward end portion defining a blade recess. The drill tool also includes a cutting blade, which is structured and arranged to be removably received in the blade recess of the tool body. The cutting blade includes a top surface, a bottom seating surface, and a plurality of side walls extending between the top surface and the bottom seating surface. A peripheral cutting edge is defined at the junction of each side wall and the top surface. Each cutting edge includes a linear cutting edge portion and a concave cutting edge portion, the concave cutting edge portion being bent inwardly in a plane perpendicular to a plane containing a central axis. A rounded corner portion connects two adjacent cutting edges. Each linear cutting edge portion extends from a rounded corner portion to a concave cutting edge portion, and each concave cutting edge portion extends from a linear cutting edge portion to another rounded corner portion.

[0012] According to one aspect of the present invention, a cutting blade includes a top surface, a bottom surface, and a plurality of side walls extending between the top surface and the bottom surface. The central axis of the cutting blade extends through the top surface and the bottom surface. A peripheral cutting edge is defined at the junction of each side wall and the top surface. Each cutting edge includes a linear cutting edge portion having an end connected to a concave cutting edge portion, wherein the concave cutting edge portion is bent inwardly in a plane perpendicular to a first plane containing the central axis, wherein at least one linear cutting edge portion and its corresponding end are parallel to the first plane containing the central axis. A rounded corner portion connects two adjacent cutting edges. Each linear cutting edge portion extends from a rounded corner portion to a concave cutting edge portion, and each concave cutting edge portion extends from a linear cutting edge portion to another rounded corner portion.

[0013] According to another aspect of the present invention, a cutting insert includes an indexable polygonal insert body having a top surface, an opposing bottom seating surface, and a plurality of side walls extending between the top surface and the bottom seating surface. The cutting insert also includes a peripheral cutting edge defined at the intersection of each side wall and the top surface, each cutting edge including a linear cutting edge portion having an end connected to a concave cutting edge portion, the concave cutting edge portion having a greater length than the linear cutting edge portion. The concave cutting edge portion is bent inwardly in a plane perpendicular to a first plane containing a central axis of the cutting insert, the central axis extending through the top surface and the bottom seating surface, wherein at least one linear cutting edge portion and its corresponding end are parallel to the first plane containing the central axis. The insert body also includes a radiused corner portion connecting two adjacent cutting edges.

[0014] According to another aspect of the present invention, a cutting insert includes an indexable polygonal insert body having a top surface, an opposing bottom seating surface, and a plurality of side walls extending between the top surface and the bottom seating surface. The cutting insert also includes a peripheral cutting edge defined at the intersection of each side wall and the top surface, each cutting edge including a linear cutting edge portion having an end connected to a concave cutting edge portion, the concave cutting edge portion having a greater length than the linear cutting edge portion. The concave cutting edge portion is bent inwardly in a plane perpendicular to a first plane containing a central axis of the cutting insert, the central axis extending through the top surface and the bottom seating surface, wherein at least one linear cutting edge portion and at least a portion of its corresponding end are parallel to the first plane containing the central axis. The insert body also includes a radiused corner portion connecting two adjacent cutting edges.

[0015] These and other aspects of the invention will be more fully understood after reading this specification and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is an isometric view of a cutting insert according to one aspect of the present invention.

[0017] Figure 2 According to one aspect of the present invention Figure 1 Top view of the cutting insert shown in .

[0018] Figure 2A According to one aspect of the present invention Figure 2 An enlarged partial top view of the corner portion.

[0019] Figure 3 According to one aspect of the present invention Figure 1 and Figure 2 Front elevation view of the cutting insert shown in .

[0020] Figure 4 According to one aspect of the present invention, Figure 1-3 0026] Figure 2 is a view of a cutting tool, such as a drill, with a cutting insert shown in FIG.

[0021] Figure 5 According to another aspect of the present invention Figure 4 An enlarged exploded view of the axially forward end of the drilling tool shown in FIG.

[0022] Figure 6 is similar to Figure 2 A top view of the invention is shown, showing further aspects of the invention. DETAILED DESCRIPTION

[0023] The following description is only for the purpose of illustrating various aspects of the present invention and is not for the purpose of limiting the scope of the present invention.

[0024] See also Figure 1 3, shows a cutting insert according to one aspect of the present invention, which is generally designated by reference numeral 10. The cutting insert 10 includes a top surface 12 (which may also be referred to as a rake face), a bottom surface 14 (which may also be referred to as a seating surface or bottom seating surface), and a plurality of side walls 16 (which may also be referred to as rear faces or relief faces) extending between the top surface 12 and the bottom surface 14. The cutting insert 10 includes a central axis AA extending through or passing through the top surface 12 and the bottom surface 14.

[0025] In one aspect, the body of the cutting insert 10 is structured and arranged as a polygon. Although a generally square cutting insert 10 with four sides is shown in the drawings for illustrative purposes only, it should be understood that other multi-sided or polygonal shapes (e.g., triangles, rectangles, pentagons, etc.) can be used for the cutting insert of the present invention. On the other hand, the body of the cutting insert 10 is structured and arranged as an indexable type cutting insert. In another aspect of the present invention, the body of the cutting insert 10 is structured and arranged so that the side wall 16 is generally inclined inwardly or obliquely from the top surface 12 to the bottom surface 14, so that the bottom surface is smaller than the top surface 14.

[0026] Still see Figure 1-3 According to another aspect of the present invention, the cutting insert 10 also includes a peripheral cutting edge 18 defined at the junction or intersection of each side wall 16 and the top surface 12. Each cutting edge 18 includes a linear cutting edge portion 18a and a concave cutting edge portion 18b. In one aspect, the concave cutting edge portion 18b is curved inwardly in a plane perpendicular to the plane containing the central axis, such as, for example Figure 2 In one example, the concave cutting edge portion 18b is curved inwardly in the plane of the top surface 12, as shown in FIG. Figure 2 As shown in the top view.

[0027] In another aspect, one or more concave cutting edge portions 18b may be curved inwardly in a plane containing one or more other concave cutting edge portions 18b.

[0028] The cutting insert 10 also includes a radiused corner portion 20 connecting two adjacent cutting edges 18. In one aspect, each radiused corner portion 20 connects the linear cutting edge portion 18a of one cutting edge 18 to the concave cutting edge portion 18b of an adjacent cutting edge 18.

[0029] The linear cutting edge portion 18a is generally a linear or straight edge extending from the corresponding radiused corner portion 20 to its intersection with the concave cutting edge portion 18b. In one aspect, the linear cutting edge portion 18a has a length L1 in the range of about 0.1 mm to about 12 mm.

[0030] The concave cutting edge portion 18b is generally a concave edge or an inwardly curved edge extending from the corresponding rounded corner portion 20 to the intersection thereof with the linear cutting edge portion 18a. In one aspect, the concave cutting edge portion 18b has a length L2 in the range of about 1 mm to about 30 mm (e.g., linearly measured from one end of the concave cutting edge portion 18b adjacent to the corresponding rounded corner portion 20 to the opposite end of the concave cutting edge portion 18b intersecting the linear cutting edge portion 18a). In one aspect, the concave cutting edge portion 18b has a length L2 greater than the length L1 of the linear cutting edge portion 18a, i.e., L2>L1. On the other hand, the ratio L2 / (L1+L2)=about 80%. In yet another aspect, the length L2 of the cutting edge portion 18b ranges from about 70% to about 90% of (L1+L2). In one example, the length L2 of the cutting edge portion 18b is about 80% of (L1+L2).

[0031] In one aspect, for various blade sizes, the length L1 of the linear cutting edge 18a varies according to the following relationship: L1 = about 20% of (L1 + L2). In other words, L1 / (L1 + L2) = about 20%. On the other hand, the length of the portion L1 of the cutting edge 18a can be in the range of about 10% to about 30% of (L1 + L2). In one example, the length of the portion L1 of the cutting edge 18a is about 20% of (L1 + L2).

[0032] In another aspect of the present invention, each side wall 16 includes a straight side wall portion or a flat side wall portion 22, which is adjacent to the linear cutting edge portion 18a and extends generally downward from the linear cutting edge portion 18a toward the bottom surface 14. The straight side wall portion 22 is a generally flat surface. In addition, the straight side wall portion 22 may extend continuously from the linear cutting edge portion 18a to the bottom surface 14, or the straight side wall portion 22 may include a lower straight side wall portion or a flat side wall portion 22a adjacent to the bottom surface 14, and the straight side wall portion or the flat side wall portion 22a may be more inclined or angled inwardly than the straight side wall portion 22 to provide, for example, a seating surface or configuration for mounting the cutting insert 10 in a cutting tool, as will be described herein.

[0033] In another aspect of the present invention, each side wall 16 also includes a concave side wall portion 24, which is adjacent to the concave cutting edge portion 18b and extends generally downward from the concave cutting edge portion 18b toward the bottom surface 14. The concave side wall portion 24 is a generally concave or inwardly curved surface. In addition, the concave side wall portion 24 can extend continuously from the concave cutting edge portion 18b to the bottom surface 14, or the concave side wall portion 24 can include a lower concave side wall portion 24a adjacent to the bottom surface 14, and the lower concave side wall portion 24a can be more inclined or slanted inwardly than the concave side wall portion 24 to provide, for example, a seating surface or configuration for mounting the cutting insert 10 in a cutting tool.

[0034] In addition, a rounded corner sidewall 26 is provided adjacent to each rounded corner portion 20, wherein the rounded corner sidewall 26 connects the concave sidewall portion 18b of one sidewall 16 with the straight sidewall portion 18a of the adjacent sidewall 16. The rounded corner sidewall 26 may extend continuously from the rounded corner portion 20 to the bottom surface 14, or the rounded corner sidewall 26 may include a lower rounded corner sidewall 26a adjacent to the bottom surface 14, and the lower rounded corner sidewall 26a may be more inclined or slanted inwardly than the rounded corner sidewall 26.

[0035] The concave cutting edge portion 18b may have a radius R1 in the range of about 1 mm to about 100 mm (see, e.g. Figure 2 The concave sidewall portion 24 may have a radius R2 in the range of about 0.8 mm to about 100 mm (see, e.g. Figure 1 ). In one aspect, the radius R2 of the concave sidewall portion 24 is substantially the same as the radius R1 of the concave cutting edge portion 18b. In another aspect, the lower concave sidewall portion 24a may also have a radius substantially the same as the radius R2 of the concave sidewall portion 24. However, it should be understood that R1, R2 and / or the radius of the lower concave sidewall portion 24a may also have different radius sizes.

[0036] The cutting edge 18 includes a top surface or portion 28 on or adjacent to the top surface 12 of the cutting insert 10. The top 28 includes a top 28a adjacent to the linear cutting edge portion 18a and a top 28b adjacent to the concave cutting edge portion 18b. These tops are contained in the same plane. In one aspect, the top 28 is contained in a single plane. In another aspect, the tops 28a and 28b are contained in the same plane to form a straight, flat or continuous top 28 of the cutting edge 18 (see, e.g., Figure 3 ).

[0037] According to another aspect of the present invention, the top surface 12 may include a chip breaker groove 30 formed therein and extending beside the cutting edge 18. The chip breaker groove 30 may extend partially or completely around the perimeter of the top surface 12. The chip breaker groove 30 includes a descending wall 32 that slopes downward from the cutting edge 18, such as from the top 28 of the cutting edge 18, to a bottom area 34 of the chip breaker groove 30, and a rear wall 36 that slopes upward from the bottom area 34 of the chip breaker groove 30. Advantageously, the chip breaker groove 30 deflects and / or bends chips being removed from the workpiece to improve the efficiency of the cutting insert 10.

[0038] The rear wall 36 of the chip breaker 30 extends upwardly to a raised central top surface 38 of the top face 12 of the cutting insert 10. In one aspect, the raised central top surface 38 rises above the cutting edge 18. The raised central top surface 38 defines a mounting opening 40 extending axially through the cutting insert 10 along the axis AA.

[0039] See also Figure 4 and Figure 5, according to one aspect of the present invention, a cutting tool, such as a drill 42, for employing or utilizing one or more cutting inserts 10 is shown. The drill 42 may include an elongated body 44 extending axially along an elongated central axis BB and including an axially rearward end 46 having a shank 48 and an axially forward end 50 defining at least one insert pocket 52. The body 44 may also include a slot 54 formed therein. The cutting insert 10 is structured and arranged to be removably received in the insert pocket 52 of the body 44. In one aspect, the cutting insert 10 is received, positioned and / or mounted in the insert pocket 52 and held in place by an insert mounting screw 56 received in the mounting opening 40 of the cutting insert 10. It should be understood that other types of cutting tools besides the drill 42 may be used in conjunction with aspects of the present invention.

[0040] Thus, it will be appreciated that the use of a combination of the linear cutting edge 18a and the concave cutting edge 18b facilitates smoother and more gradual engagement of the insert 10 into the workpiece during axial advancement of a cutting tool, such as a drill 42, toward the workpiece. At the same time, it also helps stabilize the cutting forces and minimize lateral or radial drift of the drill 42 during the cutting operation. This helps maintain the dimensional accuracy of the borehole in the workpiece within tight tolerances.

[0041] See also Figure 6 , showing something like Figure 2 But the top view illustrating another aspect of the present invention. As shown, there is a first plane XX containing the central axis AA and a second plane YY perpendicular to the first plane XX and also containing the central axis AA. In one aspect, each linear cutting edge portion 18a has an end 18c connected to a concave cutting edge portion 18b, and the concave cutting edge portion 18b is bent inwardly in a plane perpendicular to the first plane XX and / or the second plane YY.

[0042] On the other hand, at least one linear cutting edge portion 18a and its corresponding end portion 18c are parallel to a first plane XX containing the central axis AA (e.g., as shown by Figure 6 (as shown in the upper right quadrant and / or lower left quadrant defined by plane XX and plane YY).

[0043] On the other hand, the at least one linear cutting edge portion 18a is at a distance Da from the first plane XX, and its corresponding end 18c is at a distance Dc from the first plane XX, wherein Da=Dc, i.e., the at least one linear cutting edge portion 18a and its corresponding end 18c are at a distance Dc from the first plane XX (e.g., as shown by Figure 6 The diagram is equidistant from the top right quadrant and / or the bottom left quadrant defined by plane XX and plane YY).

[0044] On the other hand, at least one other linear cutting edge portion 18a and its corresponding end portion 18c are parallel to the second plane YY (e.g., as shown by Figure 6 (as shown in the upper left quadrant and / or lower right quadrant defined by plane XX and plane YY).

[0045] On the other hand, the at least one other linear cutting edge portion 18a is at a distance Da from the second plane YY, and its corresponding end 18c is at a distance Dc from the second plane YY, wherein Da=Dc, i.e., the at least one other linear cutting edge portion 18a and its corresponding end 18c are at a distance Dc from the second plane YY (e.g., as shown by Figure 6 The diagram is equidistant from the top left quadrant and / or the bottom right quadrant defined by plane XX and plane YY).

[0046] In another aspect of the present invention, the at least one linear cutting edge portion 18a and its corresponding end portion 18c (such as by Figure 6 XX and YY defined by the upper right quadrant and / or the lower left quadrant) are perpendicular to at least one other linear cutting edge portion 18a and its corresponding end 18c (as shown by Figure 6 In other words, the linear cutting edge portions 18a and their corresponding ends 18c adjacent to each other are perpendicular to each other.

[0047] In one aspect, the end 18c is a segment that substantially connects the linear cutting edge portion 18a to the concave cutting edge portion 18b. For example, the end 18c can be a point or a straight line segment.

[0048] On the other hand, the end 18c may be a curved surface or a single radius. In the aspect where the end 18c is a curved surface or a radius, only the portion of the curved surface or radius connected to 18a will be parallel to XX (or YY), or equidistant, i.e., Da=Dc. In this case where the end 18c is a curved surface or a radius, only the portion of the curved surface or radius connected to the concave cutting edge portion 18b will not satisfy Da equals Da. In one such aspect, for example, Da>Dc. Therefore, according to aspects of the present invention as shown herein, at least a portion of the end 18c may be parallel to XX (or YY), and / or equidistant, i.e., Da=Dc, etc.

[0049] Advantageously, the combination of the linear cutting edge 18a and the concave cutting edge 18b connected together by the end 18c allows the entire cutting edge 18 to be gradually inserted or entered into the workpiece. The gradual entry makes drilling smoother. Otherwise, the entry into the workpiece would not be smooth, with the entire cutting edge entering the workpiece almost instantly.

[0050] While certain aspects of the present invention have been described above for purposes of illustration, it will be apparent to those skilled in the art that numerous modifications may be made to the details of the invention without departing from the invention as defined in the appended claims.

Claims

1. A cutting insert, comprising: Top surface; a bottom surface, wherein a central axis of the cutting insert extends through the top surface and the bottom surface; a plurality of side walls extending between the top surface and the bottom surface; a peripheral cutting edge defined at the junction of each side wall and the top surface, each cutting edge including a linear cutting edge portion and a concave cutting edge portion, wherein the concave cutting edge portion is a curved edge that curves inwardly in a plane perpendicular to a plane containing the central axis; and a rounded corner portion, the rounded corner portion connecting two adjacent cutting edges, Wherein, each linear cutting edge portion extends directly from one radius corner portion to the concave cutting edge portion, and each concave cutting edge portion extends directly from the linear cutting edge portion to the other radius corner portion and curves continuously from the linear cutting edge portion to the other radius corner portion.

2. The cutting insert according to claim 1, wherein Each sidewall includes a planar sidewall portion adjacent to the linear cutting edge portion.

3. The cutting insert according to claim 2, wherein: Each sidewall also includes a concave sidewall portion adjacent the concave cutting edge portion.

4. The cutting insert according to claim 3, wherein: The concave sidewall portion has a radius that is substantially the same as a radius of the concave cutting edge portion.

5. The cutting insert of claim 3, further comprising a rounded corner sidewall adjacent to each rounded corner portion, wherein: The rounded corner sidewalls connect the concave sidewall portion of one sidewall with the flat sidewall portion of an adjacent sidewall.

6. The cutting insert according to claim 1, wherein The concave cutting edge portion has a greater length than the linear cutting edge portion.

7. The cutting insert according to claim 1, wherein The concave cutting edge portion has a length in the range of about 1 mm to about 30 mm.

8. The cutting insert according to claim 1, wherein The linear cutting edge portion has a length in the range of about 0.1 mm to about 12 mm.

9. The cutting insert according to claim 1, wherein: The concave cutting edge portion has a radius in the range of about 1 mm to about 100 mm.

10. The cutting insert according to claim 1, wherein The top surface includes a chip breaker groove formed therein and extending beside the cutting edge, the chip breaker groove including a descending wall sloping downward from the cutting edge to a bottom area of ​​the chip breaker groove and a rear wall sloping upward from the bottom area of ​​the chip breaker groove.

11. The cutting insert according to claim 10, wherein The rear wall of the chip breaker groove extends upward to the convex central top surface of the top surface of the cutting insert.

12. The cutting insert according to claim 11, wherein The raised central top surface defines a mounting opening extending axially through the cutting insert.

13. The cutting insert according to claim 1, wherein: The linear cutting edge portion and the concave cutting edge portion each include a top portion, which is contained in the same plane.

14. A cutting insert comprising: an indexable polygonal insert body having a top surface, an opposing bottom seating surface, and a plurality of side walls extending between the top surface and the bottom seating surface; a peripheral cutting edge defined at the intersection of each side wall and the top surface, each cutting edge including a linear cutting edge portion and a concave cutting edge portion immediately adjacent the linear cutting edge portion, the concave cutting edge portion having a greater length than the linear cutting edge portion, wherein the concave cutting edge portion is a curved edge that curves inwardly in a plane perpendicular to a plane containing a central axis of the cutting insert, the central axis extending through the top surface and the bottom seating surface, and wherein the entire concave cutting edge portion is curved; and The insert body also includes a radiused corner portion connecting two adjacent cutting edges.

15. The cutting insert according to claim 14, wherein Each sidewall includes a flat sidewall portion adjacent to the linear cutting edge portion and a concave sidewall portion adjacent to the concave cutting edge portion.

16. The cutting insert according to claim 14, wherein Each linear cutting edge portion extends from one radiused corner portion to the concave cutting edge portion, and each concave cutting edge portion extends from the linear cutting edge portion to the other radiused corner portion.

17. The cutting insert according to claim 14, wherein: The linear cutting edge portion and the concave cutting edge portion each include a top portion, which is contained in the same plane.

18. A drilling tool comprising: a cutter body including an axially rearward end portion having a shank and an axially forward end portion defining a blade pocket; and A cutting insert structured and arranged to be removably received in an insert pocket of a cutter body, the cutting insert comprising: Top surface; a bottom seating surface, wherein a central axis of the cutting insert passes through the top surface and the bottom seating surface; a plurality of side walls extending between the top surface and the bottom seating surface; a peripheral cutting edge defined at the junction of each side wall and the top surface, each cutting edge including a linear cutting edge portion and a concave cutting edge portion, wherein the concave cutting edge portion is a curved edge that curves inwardly in a plane perpendicular to a plane containing the central axis; and a rounded corner portion, the rounded corner portion connecting two adjacent cutting edges, Wherein, each linear cutting edge portion extends directly from one radius corner portion to the concave cutting edge portion, and each concave cutting edge portion extends directly from the linear cutting edge portion to the other radius corner portion and curves continuously from the linear cutting edge portion to the other radius corner portion.

19. The drilling tool according to claim 18, wherein Each sidewall includes a flat sidewall portion adjacent to the linear cutting edge portion and a concave sidewall portion adjacent to the concave cutting edge portion.

20. The drilling tool according to claim 18, wherein The linear cutting edge portion and the concave cutting edge portion each include a top portion, which is contained in the same plane.

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