Claims:We claim:

1. A cutting insert (10), comprising:
a first surface (12);
a second surface (14) opposite the first surface (12);
a plurality of side surfaces (16) connecting the first surface (12) and the second surface (14), each side surface (16) perpendicular to the first surface (12) and the second surface (14) such that the cutting insert (10) is a double-sided cutting insert;
a first plurality of cutting edges (18) formed at an intersection between the plurality of side surfaces (16) and the first surface (12);
a second plurality of cutting edges (18) formed at an intersection between the plurality of side surfaces (16) and the second surface (14);
a rake face (30) extending downwardly from each cutting edge (18) to a planar central region (26); and
a plurality of rounded corners (20) connecting the first and second surfaces (12, 14) and the plurality of side surfaces (16),
characterized in that:
each side surface (16) is formed with at least one concave portion (16a, 16b) extending along each cutting edge (18) and having a radius, R, for providing bottom clearance between the cutting insert (10) and a workpiece (200), and a central planar portion (16c) for engaging a pocket (116) of a cutting tool (100).

2. The cutting insert as claimed in claim 1, wherein the radius, R, is between 200 mm and 400 mm.

3. The cutting insert as claimed in claim 1, wherein the at least one concave portion (16a, 16b) has a continuously varying width.

4. The cutting insert as claimed in claim 1, wherein the central planar portion (16c) is substantially rectangular in shape.

5. The cutting insert as claimed in claim 1, wherein the second surface (14) is identical to the first surface (12).

6. The cutting insert as claimed in claim 1, wherein the cutting insert (10) comprises an indexable, double-sided, polygonal cutting insert.

7. The cutting insert as claimed in claim 1, wherein each rounded corner (20) is identical to each other.

8. The cutting insert as claimed in claim 1, wherein the concave portion (16a) of each side surface (16) has a minimum width, WMIN, proximate one of the plurality of rounded corners (20) and a maximum width, WMAX, at a highest point, P, in elevation of the cutting edge (18).

9. The cutting insert as claimed in claim 8, wherein the highest point, P, in elevation is located between 5% and 35% of a length, LCE, of the cutting edge (18).

10. The cutting insert as claimed in claim 1, wherein each cutting edge (18) has a length, LCE, and wherein the at least one concave portion (16a, 16b) has a length, LCP, smaller than the length, LCE, of each cutting edge (18).

11. An indexable, double-sided, polygonal cutting insert (10), comprising:
a first surface (12);
a second surface (14) opposite the first surface (12), the second surface (14) identical to the first surface (12);
a plurality of identical side surfaces (16) connecting the first surface (12) and the second surface (14), each side surface (16) perpendicular to the first surface (12) and the second surface (14) such that the cutting insert (10) is a double-sided cutting insert;
a plurality of identical cutting edges (18) formed at an intersection between the plurality of side surfaces (16) and the first and second surfaces (12, 14);
a rake face (30) extending downwardly from each cutting edge (18) to a planar central region (26);
a countersunk bore (22) centrally located about a central, longitudinal axis (24) of the cutting insert; and
a plurality of rounded corners (20) connecting the first and second surfaces (12, 14) and the plurality of side surfaces (16),
characterized in that:
each side surface (16) is formed with at least one concave portion (16a, 16b) extending along each cutting edge (18) and having a radius, R, for providing bottom clearance between the cutting insert (10) and a workpiece (200), and a central planar portion (16c) for engaging a pocket (116) of a cutting tool (100).

12. The cutting insert as claimed in claim 11, wherein the radius, R, is between 200 mm and 400 mm.

13. The cutting insert as claimed in claim 11, wherein the at least one concave portion (16a, 16b) has a continuously varying width.

14. The cutting insert as claimed in claim 11, wherein the central planar portion (16c) is substantially rectangular in shape.

15. The cutting insert as claimed in claim 11, wherein the concave portion (16a) of each side surface (16) has a minimum width, WMIN, proximate one of the plurality of rounded corners (20) and a maximum width, WMAX, at a highest point, P, in elevation of the cutting edge (18).

16. The cutting insert as claimed in claim 15, wherein the highest point, P, in elevation lies between 5% and 35% of a length, LCE, of the cutting edge (18).

17. The cutting insert as claimed in claim 11, wherein each cutting edge (18) has a length, LCE, and wherein the concave portion (16a, 16b) has a length, LCP, smaller than the length, LCE, of each cutting edge (18).

18. The cutting insert as claimed in claim 11, wherein the first cutting edge portion (18a) constitutes 5-15% of a length, LCE, of the cutting edge (18), and wherein the second cutting edge portion (18b) constitutes 85-95% of the length, LCE, of the cutting edge (18).

19. A cutting tool (100), comprising:
a tool body (102) having a plurality of pockets (116) for mounting an indexable, double-sided, polygonal cutting insert (10), the cutting insert comprising:
a first surface (12);
a second surface (14) opposite the first surface (12), the second surface (14) identical to the first surface (12);
a plurality of identical side surfaces (16) connecting the first surface (12) and the second surface (14), each side surface (16) perpendicular to the first surface (12) and the second surface (14) such that the cutting insert (10) is a double-sided cutting insert;
a plurality of identical cutting edges (18) formed at an intersection between the plurality of side surfaces (16) and the first and second surfaces (12, 14);
a rake face (30) extending downwardly from each cutting edge (18) to a planar central region (26);
a countersunk bore (22) centrally located about a central, longitudinal axis (24) of the cutting insert; and
a plurality of rounded corners (20) connecting the first and second surfaces (12, 14) and the plurality of side surfaces (16),
characterized in that:
each side surface (16) is formed with at least one concave portion (16a, 16b) extending along each cutting edge (18) and having a radius, R, for providing bottom clearance between the cutting insert (10) and a workpiece (200), and a central planar portion (16c) for engaging the pocket (116) of the cutting tool (100).

Dated 20th February 2020

Gopinath Arenur Shankararaj
IN/PA - 1852
OF K&S PARTNERS
AGENT FOR THE APPLICANT
, Description:FORM 2
THE PATENTS ACT, 1970
[39 of 1970]
&
THE PATENTS RULES, 2003

COMPLETE SPECIFICATION
[See Section 10 and rule 13]

TITLE: “CUTTING INSERT AND ROTARY CUTTING TOOL”

Name of the Applicant: KENNAMETAL INDIA LIMITED
Address of the Applicant: 8/9th Mile, Tumkur Road, Bangalore – 560073, Karnataka, India

Nationality: Indian

The following specification particularly describes the invention and the manner in which it is to be performed.

CUTTING INSERT WITH CONCAVE FLANK SURFACES

FIELD OF THE DISCLOSURE
[0001] The invention pertains to the field of indexable cutting inserts. More particularly, the invention pertains to an indexable, double sided, polygonal cutting insert with flank surfaces having a concave portion and a flat portion for improved bottom clearance and proper seating of the cutting insert, respectively.

BACKGROUND OF THE DISCLOSURE
[0001] Common shapes of indexable cutting inserts include square, triangular and rhombus (diamond) providing four, three and two cutting edges, respectively, on each side of the insert. A double-sided or invertible square insert, for example, can be flipped over to provide eight cutting edges.
[0002] In a 90º shoulder milling cutting insert with multiple cutting edges, for example, there is a challenge with providing sufficient bottom clearance when the indexable cutting insert is mounted on the cutting tool. In addition, sinter distortion, particularly in a “pressed and sintered to size” (PSTS) type of cutting insert and variation in powder batches significantly reduces the bottom clearance (i.e., the clearance between the cutting insert and the workpiece and, in some cases, does not provide any bottom clearance at all.
[0003] Thus, it is desirable to provide an indexable, double sided, polygonal cutting insert having improved bottom clearance, i.e., clearance between the cutting insert and the workpiece, while providing proper seating of the cutting insert.

SUMMARY OF THE DISCLOSURE

[0004] A problem of providing adequate bottom clearance in an indexable, double-sided, polygonal cutting insert can be solved by providing one or more flank surfaces that has upper and lower concave portions and a planar central portion.
[0005] In one aspect, a cutting insert comprises a first surface, a second surface opposite the first surface, and a plurality of side surfaces connecting the first surface and the second surface, each side surface perpendicular to the first surface and the second surface such that the cutting insert is a double-sided cutting insert. A first plurality of cutting edges is formed at an intersection between the plurality of side surfaces and the first surface, and a second plurality of cutting edges is formed at an intersection between the plurality of side surfaces and the second surface. A rake face extends downwardly from each cutting edge to a planar central region, and a plurality of rounded corners connect the first and second surfaces and the plurality of side surfaces. Each side surface is formed with at least one concave portion extending along each cutting edge and having a radius, R, for providing bottom clearance between the cutting insert and a workpiece, and a central planar portion for engaging a pocket of a cutting tool.
[0006] In another aspect, an indexable, double-sided, polygonal cutting insert comprises a first surface, a second surface opposite the first surface, the second surface identical to the first surface, and a plurality of identical side surfaces connecting the first surface and the second surface, each side surface perpendicular to the first surface and the second surface such that the cutting insert is a double-sided cutting insert. A plurality of identical cutting edges are formed at an intersection between the plurality of side surfaces and the first and second surfaces. A rake face extends downwardly from each cutting edge to a planar central region. A countersunk bore is centrally located about a central, longitudinal axis of the cutting insert, and a plurality of rounded corners connect the first and second surfaces and the plurality of side surfaces. Each side surface is formed with at least one concave portion extending along each cutting edge and having a radius, R, for providing bottom clearance between the cutting insert and a workpiece, and a central planar portion for engaging a pocket of a cutting tool.
[0007] In yet another aspect, a cutting tool comprises a tool body having a plurality of pockets for mounting an indexable, double-sided, polygonal cutting insert. The cutting insert comprises a first surface, a second surface opposite the first surface, and a plurality of side surfaces connecting the first surface and the second surface, each side surface perpendicular to the first surface and the second surface such that the cutting insert is a double-sided cutting insert. A plurality of identical cutting edges is formed at an intersection between the plurality of side surfaces and the first and second surfaces. A rake face extends downwardly from each cutting edge to a planar central region. A countersunk bore is centrally located about a central, longitudinal axis of the cutting insert, and a plurality of rounded corners connect the first and second surfaces and the plurality of side surfaces. Each side surface is formed with at least one concave portion extending along each cutting edge and having a radius, R, for providing bottom clearance between the cutting insert and a workpiece, and a central planar portion for engaging a pocket of a cutting tool.

BRIEF DESCRIPTION OF THE DRAWINGS
[0008] While various embodiments are illustrated, the particular embodiments shown should not be construed to limit the claims. It is anticipated that various changes and modifications may be made without departing from the scope of this disclosure.
[0009] FIG. 1 is an isometric view of a first surface of a double-sided, indexable, polygonal cutting insert according to an embodiment;
[00010] FIG. 2 is a top view of the cutting insert of FIG. 1;
[00011] FIG. 3 is a side view of the cutting insert of FIG. 1;
[00012] FIG. 4 is a front view of a cutting tool, such as a milling cutter, with the cutting insert of FIG. 1 mounted in the pockets of the cutting tool; and
[00013] FIG. 5 is an enlarged view of the cutting insert of FIG. 1 mounted in the pocket of the cutting tool.

DETAILED DESCRIPTION
[00014] Referring now to FIGS. 1-3, a cutting insert 10 is generally shown according to an embodiment. In general, the cutting insert 10 comprises an indexable, double-sided, polygonal cutting insert. Although other geometric shapes are possible, the cutting insert 10 is of a generally square shape that is symmetric about a central axis 24 and includes four cutting edges on each side for a total of eight cutting edges. However, it will be appreciated that the invention can be practiced with any multiple number of cutting edges.
[00015] Directional phrases used herein, such as, for example, left, right, front, back, top, bottom and derivatives thereof, relate to the orientation of the elements shown in the drawings and are not limiting upon the claims unless expressly recited therein. Identical parts are provided with the same reference number in all drawings.
[00016] Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about”, “approximately”, and “substantially”, are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Here and throughout the specification and claims, range limitations may be combined and/or interchanged, such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise.
[00017] Throughout the text and the claims, use of the word "about" in relation to a range of values (e.g., "about 22 to 35 wt %") is intended to modify both the high and low values recited, and reflects the penumbra of variation associated with measurement, significant figures, and interchangeability, all as understood by a person having ordinary skill in the art to which this disclosure pertains.
[00018] For purposes of this specification (other than in the operating examples), unless otherwise indicated, all numbers expressing quantities and ranges of ingredients, process conditions, etc., are to be understood as modified in all instances by the term "about". Accordingly, unless indicated to the contrary, the numerical parameters set forth in this specification and attached claims are approximations that can vary depending upon the desired results sought to be obtained by embodiments. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Further, as used in this specification and the appended claims, the singular forms "a", "an" and "the" are intended to include plural referents, unless expressly and unequivocally limited to one referent.
[00019] Notwithstanding that the numerical ranges and parameters setting forth the broad scope are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements including that found in the measuring instrument. Also, it should be understood that any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of "1 to 10" is intended to include all sub-ranges between and including the recited minimum value of 1 and the recited maximum value of 10, i.e., a range having a minimum value equal to or greater than 1 and a maximum value of equal to or less than 10. Because the disclosed numerical ranges are continuous, they include every value between the minimum and maximum values. Unless expressly indicated otherwise, the various numerical ranges specified in this application are approximations.
[00020] In the following specification and the claims, a number of terms are referenced that have the following meanings.
[00021] The singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise.
[00022] “Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not.
[00023] As used herein, “concave” is defined as curved, like a segment of the interior of a circle or hollow sphere; hollow and curved.
[00024] As used herein, “planar” is defined as flat or level.
[00025] As used herein, “flank” is defined as the side of anything, such as a three-dimensional object.
[00026] As used herein, a “very large radius” is defined as having a radius between 250 mm (9.8 inches) to about 350 mm (13.8 inches).
[00027] Referring now to FIGS. 1-3, the cutting insert 10 includes a first surface 12, a second surface 14 opposite the first surface 12 and a plurality of flank or side surfaces 16 connecting the first surface 12 and the second surface 14. Although not shown in FIG. 1, the second surface 14 is identical to the first surface 12, and the flank surfaces 16 are identical to each other. Thus, the cutting insert 10 is symmetric about all three axes (x-, y-, z-), and therefore only the first surface 12 will be described in detail herein for brevity. However, it will be appreciated that any discussion of the first surface 12 applies to the second surface 14, and any discussion of the flank surface 16 applies to the other flank surfaces 16.
[00028] In general, each side surface 16 (only two are shown in FIG. 1) is substantially perpendicular to both the first and second surfaces 12, 14. In other words, the first and second surfaces 12, 14 are substantially parallel to each other and perpendicular to the side surfaces 16. That is, the side surfaces 16 have a facet clearance angle of zero degrees. Thus, both the first and second surfaces 12, 14 of the cutting insert 10 can be presented to a workpiece 200 (FIG. 5). In the illustrated embodiment, the cutting insert 10 has a total of four identical side surfaces 16. Thus, only one side surface 16 will be described herein for brevity, and it will be appreciated that any description herein of one of the side surfaces 16 applies to all the side surfaces 16.
[00029] A cutting edge 18 is formed at the intersection between the first surface 12 and each side surface 16 for a total of four cutting edges 18. In addition, a cutting edge 18 is formed at the intersection between the second surface 14 and each side surface 16 for a total of four additional cutting edges 18 (i.e. a total of eight cutting edges 18 for the cutting insert 10). Each cutting edge 18 is identical to each other. Thus, only one cutting edge 18 will be described herein for brevity, and it will be appreciated that any description herein of one cutting edge 18 applies to all the cutting edges 18.
[00030] As shown in FIG. 3, each cutting edge 18 has a first cutting edge portion 18a that slopes upwardly with respect to the horizontal axis (i.e., x-axis), and a second cutting edge portion 18b that slopes downwardly with respect to the horizontal axis. The first cutting edge portion 18a has a curved profile, while the second cutting edge portion 18b has a substantially linear profile. As can be seen in FIG. 3, the first cutting edge portion 18a constitutes about 5-25% of a length, LCE, of the cutting edge 18, while the second cutting edge portion 18b constitutes about 75-95% of the length, LCE, of the cutting edge 18. As can also be seen in FIG. 3, the cutting edge 18 has a highest point, P, in elevation that is located along the cutting edge 18 between adjacent rounded corners 20. Specifically, the highest point, P, in elevation is located between about 5% and about 35% along the length, LCE, of the cutting edge 18 between adjacent rounded corners 20.
[00031] A rounded corner 20 connects adjacent side surfaces 16 and also connects the first surface 12 and the second surface 14. As shown, one rounded corner 20 is proximate the first cutting edge portion 18a and an adjacent rounded corner 20 is proximate the second cutting edge portion 18b. Preferably, each rounded corner 20 is formed with a radius in the range between approximately 0.4 mm (0.02 inches) to approximately 3.2 mm (0.13 inches). For example, the rounded corner 20 may have a radius of about 0.8 mm (0.031 inches). Because each rounded corner 20 is substantially identical to each other, only one rounded corner 20 is discussed herein for brevity, and it will be appreciated that any description herein of one rounded corner 20 applies to all rounded corners 20.
[00032] The cutting insert 10 also includes a countersunk bore 22 extending entirely between the first and second surfaces 12, 14, and is centrally located with respect to a central, longitudinal axis 24 (i.e., the z-axis). It should be appreciated that the cutting insert is mirror symmetric about all three axes (x-, y- and z-axes). As a result, the cutting insert 10 comprises a double-sided cutting insert in which all eight cutting edges 18 at the intersection between the side surfaces 16 and each of the first and second surfaces 12, 14 are identical to each other and can separately be used in a machining operation.
[00033] The first surface 12 (and the second surface 14) has a topography that includes a substantially planar central region 26 surrounding the countersunk bore 22. The central region 26 extends from the countersunk bore 22 and terminates in an irregular-shaped boundary 28. As mentioned earlier, each side surface 16 is substantially perpendicular to both the first and second surfaces 12, 14. More specifically, the substantially planar central region 26 of the first and second surfaces 12, 14 are substantially parallel to each other and perpendicular to the side surfaces 16. The first surface 12 also includes a rake face 30 extending radially inward from each cutting edge 18 to the irregular-shaped boundary 28. As shown in FIGS. 1 and 2, each rake face 30 slopes upwardly from the central region 26 to the cutting edge 18 (i.e., each rake face 30 slopes downwardly from the cutting edge 18 to the boundary 28). In other words, each rake face 30 is higher in elevation than the central region 26. The central region 26 may include unique indicia 32 to identify the cutting edge 18 being used in a cutting operation. The indicia 32 is optional and can be eliminated, if desired.
[00034] In one aspect, each flank or side surface 16 comprises an upper concave portion 16a extending along the cutting edge 18, a lower concave portion 16b extending along the cutting edge 18, and a central planar portion 16c disposed between the upper and lower concave portions 16a. It should be noted that the words “upper” and “lower” are relative terms, and the “upper” concave portion 16a becomes the “lower” concave portion 16b when the cutting insert 10 is flipped upside down (i.e., rotated 180 degrees about the x-axis) from the orientation shown in the illustrated embodiment.
[00035] It should also be noted that the central planar portion 16c comprises about 30-60% of the total surface area of the side surface 16 and is substantially rectangular in shape. However, it should be appreciated that the invention is not limited by the shape of the central planar portion 16c, and that the invention can be practiced with any desirable shape, so long as the central planar portion 16c sufficiently engages the side walls of the insert pocket to securely hold the cutting insert in the insert pocket (FIGS. 4 and 5).
[00036] In the illustrated embodiment shown in FIGS. 1-3, each of the first and second surfaces 12, 14 of the cutting insert 10 includes a wiper facet 19. As a result, each concave portion 16a, 16b has a length, LCP, that is slightly smaller than the length, LCE, of the cutting edge 18. In one embodiment, for example, the cutting edge 18 can have a length, LCE, of about 10.4 mm (0.409 inches), while each concave portion 16a, 16b has a length, LCE, of about 9.75 mm (0.384 inches). However, it will be appreciated that a length, LCP, of each concave portion 16a, 16b can be equal to the length, LCE, of the cutting edge 18 in the case where the cutting insert 10 does not have a wiper facet 19.
[00037] Because the cutting edge 18 has a curved or wavy profile when viewed from the side as seen in FIG. 3, each concave portion 16a, 16b has a minimum width, WMIN, proximate one of the rounded corners 20 and a maximum width, WMAX, at the highest point, P, in elevation of the cutting edge 18. In addition, the width, W, of each concave portion 16a continuously varies along the length, LCE, of the cutting edge 18.
[00038] Referring to FIG. 1, each concave portion 16a is formed with a very large radius, R. In one embodiment, the radius, R, is in a range between about 200 mm (8.0 inches) to about 400 mm (6.0 inches), depending on the application and the capability of the milling cutter. For example, in one embodiment, the radius, R, is about 320 mm (12.6 inches).
[00039] Referring now to FIGS. 4 and 5, a cutting tool 100, for example, a milling cutter, is shown according to an embodiment of the disclosure. The milling cutter 100 comprises a tool body 112 including a cutting end 114 with a plurality of circumferentially spaced pockets 116, and a mounting end 118 opposite the cutting end 114. The tool body 112 is designed to be rotatably driven about a central longitudinal axis 113. In the illustrated embodiment, the milling cutter 100 is commonly known as a right-hand milling cutter and includes a total of four pockets 116. However, it will be appreciated that the invention is not limited by the number of pockets 116, and that the invention can be practiced with any desirable number of pockets that provide the desired cutting capabilities. Each of the pockets 116 are capable of receiving the cutting insert 10, which is securely held in the pocket 116 by means of a mounting screw 119.
[00040] The central planar portion 16c of two side surfaces 16 of the cutting insert 10 and the planar central region 26 of one of the first and second surfaces 12, 14 to make three-point contact with the pocket 116 when the cutting insert 10 is properly mounted in the pocket 116 during cutting operations. It will be appreciated that each of the cutting edges 18 can be indexed into an active position and effectively utilized in the milling cutter 100 (FIGS. 4 and 5). It will be appreciated that the number of cutting edges 18 and the number of times that the cutting insert 10 can be indexed depends on the geometric shape of the cutting insert 10. In general, the number of times the cutting insert 10 can be indexed is equal to the total number of cutting edges 18. Thus, the cutting insert 10 can be indexed eight times, unlike conventional single-sided rectangular or square cutting inserts that can be indexed at most only four times because of the fewer number of cutting edges.
[00041] Referring to FIG. 5, the cutting insert 10 can be mounted in a respective pocket 116 of the milling cutter 100 such that the desired cutting edge 18 contacts the workpiece 200. In one embodiment, the cutting edge 18 produces a rough cut of the workpiece 200.
[00042] Measurements indicate that the upper and lower concave portions 16a, 16b of the cutting insert 10 of the disclosure provides an outside bottom clearance 34 of about 0.101 mm and an inside bottom clearance 36 of about 0.116 mm. Measurements also indicate that a conventional cutting insert having a planar flank surface produces an outside bottom clearance of about 0.086 mm and an inside bottom clearance of about 0.029 mm. As a result, the cutting insert 10 of the disclosure provides superior bottom clearance, as compared to conventional cutting inserts having a substantially planar side or flank surface. It should be noted that the outside bottom clearance 34 was measured proximate the first curved portion 18a of the cutting edge 18, and the inside bottom clearance 36 was measured along the horizontal axis (i.e., y-axis) passing through the central, longitudinal axis 24 of the cutting insert 10, as shown in FIG. 5.
[00043] In addition, measurements indicate that the upper and lower concave portions 16a, 16b of the cutting insert 10 of the disclosure provides an outside 90º wall accuracy 38 of about 0.037 mm, and an identical inside 90º wall accuracy 40 of about 0.037 mm. As a result, the cutting insert 10 of the disclosure also provides superior 90º wall accuracy. It should be noted that the outside 90º wall accuracy 38 was measured proximate the rounded corner 20, and the inside 90º wall accuracy 40 was measured along the horizontal axis (i.e., x-axis) passing through the central, longitudinal axis 24 of the cutting insert 10, as shown in FIG. 5.
[00044] Having described presently preferred embodiments the invention may be otherwise embodied within the scope of the appended claims.

REFERRAL NUMERAL
10 cutting insert
12 first surface
14 second surface
16 flank surface
16a upper concave portion
16b lower concave portion
16c central planar portion
18 cutting edge
18a first curved portion
18b second linear portion
19 wiper facet
20 curved corner
22 countersunk bore
24 central, longitudinal axis
26 planar central region
28 boundary
30 rake face
32 indicia
34 outside bottom clearance
36 inside bottom clearance
38 outside wall accuracy
40 inside wall accuracy

100 cutting tool
112 tool body
113 central, longitudinal axis
114 cutting end
116 pocket
118 mounting end
119 mounting screw

200 workpiece

WMIN minimum width
WMAX maximum width
R radius
P point
LCE length (cutting edge)
LCE length (concave portion)