Claims:WHAT IS CLAIMED IS:

1. A cutting insert comprising:
a top surface;
a bottom surface having a smaller surface area than the top surface;
four side surfaces adjoining the top surface and the bottom surface; and
four cutting edges at the intersection of each of the side surfaces and the top surface defining four corner edge portions at intersections between adjacent cutting edges, each of the cutting edges comprising:
a nose portion comprising:
a first nose segment located radially away from a first one of the corner edge portions adjacent to a central longitudinal rotational axis of a drilling body when the drilling insert is mounted in the drilling body at a first nose segment angle with respect to a reference plane bisecting a mounting through hole;
a second nose segment located radially away from the central longitudinal rotational axis of the drilling body in relation to the first nose segment at a second nose segment angle with respect to the reference plane; and
a convex corner connecting the first nose segment to the second nose segment.

2. The cutting insert of Claim 1, wherein the first nose segment and the second nose segment are linear.

3. The cutting insert of Claim 1, wherein the first nose segment angle is a positive angle with respect to the reference plane ranging from about 5 to about 35 degrees.

4. The cutting insert of Claim 1, wherein the second nose segment angle is a negative angle with respect to the reference plane ranging from about 5 to about 35 degrees.

5. The cutting insert of Claim 1, wherein an apex of the convex corner of the nose portion is bisected by a vertical reference plane bisecting the mounting through hole normal to the reference plane.
6. The cutting insert of Claim 5, wherein the apex of the convex corner of the nose portion is the farthest point of the cutting edge from a central axis of the mounting through hole.

7. The cutting insert of Claim 1, wherein each of the cutting edges are mirror symmetric with respect to a vertical reference plane bisecting the mounting through hole normal to the reference plane.

8. The cutting insert of Claim 1, wherein each of the cutting edges are not mirror symmetric with respect to a vertical reference plane bisecting the mounting through hole normal to the reference plane.

9. The cutting insert of Claim 1, wherein each of the cutting edges further comprise a first cutting edge segment extending from the first one of the corner edge portions to the first nose segment at a first cutting edge angle with respect to the reference plane, and wherein the first cutting edge segment and the first nose segment are joined together by a first transitional nose segment, the first transitional nose segment forming a convex curve with the first cutting edge segment and a concave curve with the first nose segment.

10. The cutting insert of Claim 9, wherein the second nose segment extends to a second one of the corner edge portions.

11. The cutting insert of Claim 9, wherein the each cutting edges further comprise a second cutting edge segment extending from the second nose segment to a second one of the corner edge portions at a second cutting edge angle with respect to the reference plane, and wherein the second nose segment and the second cutting edge segment are joined together by a second transitional nose segment, the second transitional nose segment forming a concave curve with the second nose segment and a convex curve with the second cutting edge segment.

12. The cutting insert of Claim 1, wherein each of the cutting edges further comprise:
a first cutting edge segment extending from the first one of the corner edge portions at a first cutting edge angle with respect to the reference plane; and
a second cutting edge segment extending from the first cutting edge segment to the first nose segment at a second cutting edge angle with respect to the reference plane.

13. The cutting insert of Claim 12, wherein the first cutting edge segment and the second cutting edge segment are joined together by a first transitional cutting edge segment, the first transitional cutting edge segment forming a convex curve with the first cutting edge segment and a concave curve with the second cutting edge segment; and the second cutting edge segment and the first nose segment are joined together by a first transitional nose segment, the first transitional nose segment forming a convex curve with the second cutting edge segment and a concave curve with the first nose segment.

14. The cutting insert of Claim 12, wherein each of the cutting edges further comprise a third cutting edge extending from the second nose segment to a second one of the corner edge portions at a third cutting edge angle with respect to the reference plane, wherein the second nose segment and the third cutting edge segment are joined together by a second transitional nose segment, the second transitional nose segment forming a concave curve with the second nose segment and a convex curve with the third cutting edge segment.

15. The cutting insert of Claim 12, wherein each of the cutting edges further comprise:
a third cutting edge extending from the second nose segment at a third cutting edge angle with respect to the reference plane, wherein the second nose segment and the third cutting edge segment are joined together by a second transitional nose segment, the second transitional nose segment forming a concave curve with the second nose segment and a convex curve with the third cutting edge segment; and
a fourth cutting edge segment extending from the third cutting edge segment to a second one of the corner edge portions at a fourth cutting edge angle with respect to the reference plane, wherein the third cutting edge segment and the fourth cutting edge segment are joined together by a second transitional cutting edge segment, the second transitional cutting edge segment forming a concave curve with the third cutting edge segment and a convex curve with the fourth cutting edge segment.

16. The cutting insert of Claim 1, wherein each side surface comprises a first clearance face extending from the top surface, a second clearance face extending from the first clearance face, and a third clearance face extending from the second clearance face to the bottom surface, and a height of the first clearance face is less than or equal to the height of the second clearance face and the third clearance face.

17. The cutting insert of Claim 1, wherein the first clearance face is located radially away from an axis of rotation of the cutting insert in relation to the second clearance face.

18. The cutting insert of Claim 16, wherein the first clearance face forms a first clearance angle ranging from about 1 to 30 degrees with respect to an axis of rotation of the cutting insert, the second clearance face forms a second clearance angle ranging from about 2.5 to about 30 degrees with respect to the axis of rotation of the cutting insert, and the third clearance face forms a third clearance angle ranging from about 5 to about 60 degrees with respect to the axis of rotation of the cutting insert.

19. The cutting insert of Claim 18, wherein the first clearance face and the second clearance face are joined together by a transition clearance, the transition clearance forming a transition angle with respect to the axis of rotation of the cutting insert, and wherein the transition angle is greater than the first clearance angle and the second clearance angle.

20. A drilling tool system comprising:
a drilling body having a central longitudinal rotational axis, and comprising an interior pocket in a front drilling face, the interior pocket comprising:
a rear surface; and
a first sidewall portion extending forward from the rear surface; and
a central drilling insert mounted in the interior pocket of the drilling body, the central drilling insert comprising:
a top surface;
a bottom surface having a smaller surface area than the top surface;
four side surfaces adjoining the top surface and the bottom surface, the four side surfaces structured and arranged to engage the rear surface and the first sidewall portion of the interior pocket of the drilling body; and
four cutting edges at the intersection of each of the side surfaces and the top surface defining four corner edge portions at intersections between adjacent cutting edges, each of the cutting edges comprising:
a nose portion comprising:
a first nose segment located radially away from a first one of the corner edge portions adjacent to the central longitudinal rotational axis of the drilling body when the drilling insert is mounted in the drilling body at a first nose segment angle with respect to a reference plane bisecting a mounting through hole;
a second nose segment located radially away from the central longitudinal rotational axis of the drilling body in relation to the first nose segment at a second nose segment angle with respect to the reference plane; and
a convex corner connecting the first nose segment to the second nose segment.

21. The drilling tool system of Claim 20, wherein the drilling body further comprises a peripheral pocket in the front drilling face structured and arranged to receive a peripheral insert, the peripheral insert having at least one cutting edge.

22. The drilling tool system of Claim 20, wherein each of the cutting edges further comprises a first cutting edge segment extending from the first one of the corner edge portions to the first nose segment at a first cutting edge angle with respect to the reference plane, and the first cutting edge segment and the first nose segment are joined together by a first transitional nose segment, the first transitional nose segment forming a convex curve with the first cutting edge segment and a concave curve with the first nose segment.

Dated this 20th day of November 2019

GOPINATH A S
IN/PA 1852
OF K&S PARTNERS
AGENT FOR THE APPLICANT
, Description: