Patent ID: 11911830
Assignee: KENNAMETAL INDIA LTD.
Field: Machine tools (Mechanical engineering)
Classification: CPC B | IPC B

Claim 18:
19. 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 capable of being received in the interior pocket of the drilling body and a peripheral cutting insert capable of being received in a peripheral 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 first cutting edge segment extending from a first one of the corner edge portions adjacent to the central longitudinal rotational axis of the drilling body at a first cutting edge angle with respect to a reference plane passing through the center of adjacent corner edge portions and parallel to an axis of rotation of the drilling insert;
a second cutting edge segment located radially away from the central longitudinal rotational axis of the drilling body in relation to the first cutting edge segment at a second cutting edge angle with respect to the reference plane; and
a third cutting edge segment extending from the second cutting edge segment at a third cutting edge angle with respect to the reference plane to a second one of the corner edge portions,

wherein the third cutting edge segment has a length, L3, equal to LC*[(DCL−DCS)], where
LC is in a range between 0.25 to 0.85,
DCL is a largest cutting diameter that will be used with the central drilling insert, and
DCS is a smallest cutting diameter that will be used with the central drilling insert, thereby allowing the central drilling insert to perform substantially an equal amount of cutting than the peripheral drilling insert.