Cutting insert and indexable edge rotary cutting tool

1. A cutting insert to be detachably mounted on a tip portion of a tool main body rotatable around a rotation axis by using a fixing member, the cutting insert comprising:

a main surface formed in a substantially parallelogram shape in a plan view and having a pair of acute angle corner portions and a pair of obtuse angle corner portions;

a seating surface that faces a side opposite to the main surface;

a side surface that connects the main surface and the seating surface to each other;

a corner cutting edge disposed in the acute angle corner portion; and

a main cutting edge and a subsidiary cutting edge which are respectively disposed in a pair of side ridge portions of the main surface located each other across the acute angle corner portion,

wherein a mounting hole into which the fixing member is to be inserted penetrates the main surface and the seating surface,

wherein the main cutting edge is inclined at an inclination angle equal to or larger than 8° with reference to a plane perpendicular to an axial direction of the mounting hole so as to be closer to a seating surface side in a direction from the acute angle corner portion toward the obtuse angle corner portion,

wherein the main surface has a region inclined in a direction away from the seating surface in a direction from the obtuse angle corner portion toward an edge portion of the mounting hole along a diagonal line connecting the pair of obtuse angle corner portions to each other,

wherein in a cross section along the diagonal line connecting the pair of obtuse angle corner portions to each other, the main surface has a projection portion projecting upward from a straight line connecting the obtuse angle corner portion and the edge portion of the mounting hole to each other,

wherein when viewed in the axial direction of the mounting hole, the projection portion is located on the diagonal line, and

wherein a foot portion of the projection portion on an obtuse angle corner portion side and a foot portion of the projection portion on a mounting hole side are located closer to the seating surface than the straight line.

2. The cutting insert according to claim 1 ,

wherein when viewed in the axial direction of the mounting hole, the projection portion overlaps a side ridge portion of the seating surface, or is located inside the side ridge portion of the seating surface.

3. The cutting insert according to claim 1 ,

wherein the main surface has a rake face of the main cutting edge, and

wherein a rake angle of the rake face is inclined to a positive angle side in an end portion on an acute angle corner portion side of the main cutting edge, and gradually increases to a negative angle side in a direction from the end portion on the acute angle corner portion side toward an end portion on an obtuse angle corner portion side, and is inclined to the negative angle side in the end portion on the obtuse angle corner portion side.

4. The cutting insert according to claim 3 ,

wherein a change point where the rake angle of the rake face is changed from inclination to the positive angle side to inclination to the negative angle side is located close to the obtuse angle corner portion in a longitudinal direction of the main cutting edge.

5. The cutting insert according to claim 1 ,

wherein when a distance from the seating surface along the axial direction of the mounting hole in an end portion on an acute angle corner portion side of the main cutting edge is set as L1, and

when a distance from the seating surface along the axial direction of the mounting hole in an end portion on an obtuse angle corner portion side of the main cutting edge is set as L2, relationships expressed by the following equations are satisfied

0.4≤ L 2/ L 1≤0.7

2.0 mm≤ L 2≤3.9 mm.

6. An indexable edge rotary cutting tool comprising:

a tool main body rotatable around a rotation axis;

a mounting seat formed in a tip portion of the tool main body in an axial direction of the rotation axis; and

a cutting insert detachably mounted on the mounting seat and having a corner cutting edge, a main cutting edge and a subsidiary cutting edge,

wherein as the cutting insert, the cutting insert according to claim 1 is used, and

wherein a rake angle in an axial direction of the main cutting edge of the cutting insert when mounted to the indexable edge rotary cutting tool's mounting seat is equal to or larger than 15°.

7. The cutting insert according to claim 2 ,

wherein the main surface has a rake face of the main cutting edge, and

wherein a rake angle of the rake face is inclined to a positive angle side in an end portion on an acute angle corner portion side of the main cutting edge, and gradually increases to a negative angle side in a direction from the end portion on the acute angle corner portion side toward an end portion on an obtuse angle corner portion side, and is inclined to the negative angle side in the end portion on the obtuse angle corner portion side.

8. The cutting insert according to claim 7 ,

wherein a change point where the rake angle of the rake face is changed from inclination to the positive angle side to inclination to the negative angle side is located close to the obtuse angle corner portion in a longitudinal direction of the main cutting edge.

9. The cutting insert according to claim 2 ,

wherein when a distance from the seating surface along the axial direction of the mounting hole in an end portion on an acute angle corner portion side of the main cutting edge is set as L1, and

when a distance from the seating surface along the axial direction of the mounting hole in an end portion on an obtuse angle corner portion side of the main cutting edge is set as L2, relationships expressed by the following equations are satisfied

0.4≤ L 2/ L 1≤0.7

2.0 mm≤ L 2≤3.9 mm.

10. The cutting insert according to claim 3 ,

wherein when a distance from the seating surface along the axial direction of the mounting hole in an end portion on an acute angle corner portion side of the main cutting edge is set as L1, and

when a distance from the seating surface along the axial direction of the mounting hole in an end portion on an obtuse angle corner portion side of the main cutting edge is set as L2, relationships expressed by the following equations are satisfied

0.4≤ L 2/ L 1≤0.7

2.0 mm≤ L 2≤3.9 mm.

11. The cutting insert according to claim 4 ,

wherein when a distance from the seating surface along the axial direction of the mounting hole in an end portion on an acute angle corner portion side of the main cutting edge is set as L1, and

when a distance from the seating surface along the axial direction of the mounting hole in an end portion on an obtuse angle corner portion side of the main cutting edge is set as L2, relationships expressed by the following equations are satisfied

0.4≤ L 2/ L 1≤0.7

2.0 mm≤ L 2≤3.9 mm.

12. The cutting insert according to claim 7 ,

wherein when a distance from the seating surface along the axial direction of the mounting hole in an end portion on an acute angle corner portion side of the main cutting edge is set as L1, and

when a distance from the seating surface along the axial direction of the mounting hole in an end portion on an obtuse angle corner portion side of the main cutting edge is set as L2, relationships expressed by the following equations are satisfied

0.4≤ L 2/ L 1≤0.7

2.0 mm≤ L 2≤3.9 mm.

13. The cutting insert according to claim 8 ,

wherein when a distance from the seating surface along the axial direction of the mounting hole in an end portion on an acute angle corner portion side of the main cutting edge is set as L1, and

when a distance from the seating surface along the axial direction of the mounting hole in an end portion on an obtuse angle corner portion side of the main cutting edge is set as L2, relationships expressed by the following equations are satisfied

0.4≤ L 2/ L 1≤0.7

2.0 mm≤ L 2≤3.9 mm.

14. An indexable edge rotary cutting tool comprising:

a tool main body rotatable around a rotation axis;

a mounting seat formed in a tip portion of the tool main body in an axial direction of the rotation axis; and

a cutting insert detachably mounted on the mounting seat and having a corner cutting edge, a main cutting edge and a subsidiary cutting edge,

wherein, as the cutting insert, the cutting insert according to claim 2 is used, and

wherein a rake angle in an axial direction of the main cutting edge of the cutting insert when mounted to the indexable edge rotary cutting tool's mounting seat is equal to or larger than 15°.

15. An indexable edge rotary cutting tool comprising:

a tool main body rotatable around a rotation axis;

a mounting seat formed in a tip portion of the tool main body in an axial direction of the rotation axis; and

a cutting insert detachably mounted on the mounting seat and having a corner cutting edge, a main cutting edge and a subsidiary cutting edge,

wherein as the cutting insert, the cutting insert according to claim 3 is used, and

wherein a rake angle in an axial direction of the main cutting edge of the cutting insert when mounted to the indexable edge rotary cutting tool's mounting seat is equal to or larger than 15°.

16. An indexable edge rotary cutting tool comprising:

a tool main body rotatable around a rotation axis;

a mounting seat formed in a tip portion of the tool main body in an axial direction of the rotation axis; and

a cutting insert detachably mounted on the mounting seat and having a corner cutting edge, a main cutting edge and a subsidiary cutting edge,

wherein as the cutting insert, the cutting insert according to claim 4 is used, and

wherein a rake angle in an axial direction of the main cutting edge of the cutting insert when mounted to the indexable edge rotary cutting tool's mounting seat is equal to or larger than 15°.

17. An indexable edge rotary cutting tool comprising:

a tool main body rotatable around a rotation axis;

a mounting seat formed in a tip portion of the tool main body in an axial direction of the rotation axis; and

a cutting insert detachably mounted on the mounting seat and having a corner cutting edge, a main cutting edge and a subsidiary cutting edge,

wherein as the cutting insert, the cutting insert according to claim 5 is used, and

wherein a rake angle in an axial direction of the main cutting edge of the cutting insert when mounted to the indexable edge rotary cutting tool's mounting seat is equal to or larger than 15°.

18. An indexable edge rotary cutting tool comprising:

a tool main body rotatable around a rotation axis;

a mounting seat formed in a tip portion of the tool main body in an axial direction of the rotation axis; and

a cutting insert detachably mounted on the mounting seat and having a corner cutting edge, a main cutting edge and a subsidiary cutting edge,

wherein as the cutting insert, the cutting insert according to claim 7 is used, and

wherein a rake angle in an axial direction of the main cutting edge of the cutting insert when mounted to the indexable edge rotary cutting tool's mounting seat is equal to or larger than 15°.

19. An indexable edge rotary cutting tool comprising:

a tool main body rotatable around a rotation axis;

a mounting seat formed in a tip portion of the tool main body in an axial direction of the rotation axis; and

a cutting insert detachably mounted on the mounting seat and having a corner cutting edge, a main cutting edge and a subsidiary cutting edge,

wherein as the cutting insert, the cutting insert according to claim 8 is used, and

wherein a rake angle in an axial direction of the main cutting edge of the cutting insert when mounted to the indexable edge rotary cutting tool's mounting seat is equal to or larger than 15°.

20. An indexable edge rotary cutting tool comprising:

a tool main body rotating rotatable around a rotation axis;

a mounting seat formed in a tip portion of the tool main body in an axial direction of the rotation axis; and

a cutting insert detachably mounted on the mounting seat and having a corner cutting edge, a main cutting edge and a subsidiary cutting edge,

wherein as the cutting insert, the cutting insert according to claim 9 is used, and

wherein a rake angle in an axial direction of the main cutting edge of the cutting insert when mounted to the indexable edge rotary cutting tool's mounting seat is equal to or larger than 15°.