Cutting insert having a corner recess
A cutting insert for a machining tool has a structure capable of effectively controlling chips generated on a work-piece. The cutting insert includes an upper surface, a lower surface, a plurality of side surfaces connecting the upper surface and the lower surface and a central hole formed at a central portion thereof. In the cutting insert, a seating surface is formed on a highest portion of the upper surface, a plurality of side cutting edge portions are formed at border portions of the upper surface and the side surfaces. Each side cutting edge portion has a side cutting edge formed at an upper end thereof and a corner cutting edge portion is formed at an intersection of two adjacent side cutting edge portions. The corner cutting edge portion has a cutting edge formed at a front end thereof, a land portion, a downward inclined surface, a corner bottom surface, a first upward inclined surface, a first protrusion, a second upward inclined surface, a second protrusion, an upward grooved surface and the seating surface sequentially formed along a diagonal line directed from the corner cutting edge toward the central hole. The corner bottom surface has the smallest height along the diagonal line.
1. A cutting insert including:
an upper surface, a lower surface, a plurality of side surfaces connecting the upper surface and the lower surface and a central hole formed at a central portion thereof, the side surfaces lying on an imaginary polygon, wherein:
a flat seating surface is formed on a highest portion of the upper surface,
a plurality of side cutting edge portions are formed at border portions of the upper surface and the side surfaces, each side cutting edge portion has a side cutting edge formed at an upper end thereof,
a corner cutting edge portion is formed at a border portion of two adjacent side cutting edge portions, the corner cutting edge portion has a corner cutting edge formed at a front end thereof,
a land portion, a downward inclined surface, a corner bottom surface, a first upward inclined surface, a first protrusion, a second upward inclined surface, a second protrusion, an upward grooved surface and the seating surface are sequentially formed along a diagonal line directed from the corner cutting edge toward the central hole, and
the corner bottom surface has the smallest height along the diagonal line.
2. The cutting insert according to claim 1 , wherein:
the first protrusion has a height smaller than that of the corner cutting edge, and
the second protrusion has a height larger than that of the corner cutting edge.
3. The cutting insert according to claim 1 , wherein:
the side cutting edge repeatedly descends and ascends starting from the corner cutting edge so that the side cutting edge has a serrated shape in which raised portions and depressed portions are alternatingly disposed.
4. The cutting insert according to claim 3 , wherein the raised portions and the depressed portions of the side cutting edge extend from the side cutting edge toward an inside of the cutting insert, and are followed by a land portion, a downward inclined surface, a side bottom surface and an upward grooved surface.
5. The cutting insert according to claim 4 , wherein the side bottom surface of the raised portion has a width larger than that of the side bottom surface of the depressed portion.
6. The cutting insert according to claim 4 , wherein:
the depressed portion adjacent to the corner cutting edge has an upward inclined surface and an extended protrusion disposed between the side bottom surface and the upward grooved surface, and
the extended protrusion extends from the second protrusion in parallel to the side cutting edge and has a height smaller than that of the second protrusion.
7. The cutting insert according to claim 6 , wherein:
a corner ridge is formed at a border of the corner cutting edge and the depressed portion adjacent to the corner cutting edge, and
the corner ridge has a height equal to or smaller than that of the side cutting edge and higher than that of the corner bottom surface.
8. The cutting insert according to claim 7 , wherein:
the corner ridge extends toward the first protrusion but falls short of the first protrusion to have a gap therebetween.
9. The cutting insert according to claim 4 , wherein:
a corner ridge is formed at a border of the corner cutting edge and a depressed portion adjacent to the corner cutting edge; and
the corner ridge has a height equal to or smaller than that of the side cutting edge and higher than that of the corner bottom surface.
10. The cutting insert according to claim 9 , wherein:
the corner ridge extends toward the first protrusion but falls short of the first protrusion to have a gap therebetween.
11. The cutting insert according to claim 10 , wherein:
the first protrusion has a height smaller than that of the corner cutting edge, and
the second protrusion has a height larger than that of the corner cutting edge.
12. The cutting insert according to claim 4 , wherein:
the side bottom surface of the raised portion is farther from its associated side cutting edge than the side bottom surface of the depressed portion is from its own associated side cutting edge.
13. The cutting insert according to claim 12 , wherein:
the first protrusion has a height smaller than that of the corner cutting edge, and
the second protrusion has a height larger than that of the corner cutting edge.
14. The cutting insert according to claim 12 , wherein:
the depressed portion adjacent to the corner cutting edge has an upward inclined surface and an extended protrusion disposed between the side bottom surface and the upward grooved surface;
the extended protrusion extends from the second protrusion in parallel to the side cutting edge and has a height smaller than that of the second protrusion;
a corner ridge is formed at a border of the corner cutting edge and a depressed portion adjacent to the corner cutting edge;
the corner ridge has a height equal to or smaller than that of the side cutting edge and higher than that of the corner bottom surface; and
the corner ridge extends toward the first protrusion but falls short of the first protrusion to have a gap therebetween.
15. The cutting insert according to claim 14 , wherein:
the first protrusion has a height smaller than that of the corner cutting edge, and
the second protrusion has a height larger than that of the corner cutting edge.