Cutting insert and cutting tool on which same is mounted

1 . A cutting insert comprising an upper surface, a lower surface, a lateral surface, a cutting edge, and a fastening hole, wherein

the cutting edge includes a main cutting edge, a nose R part connected to the main cutting edge, and a sub-cutting edge connected to the nose R part,

the upper surface includes a land part adjacent to the cutting edge, an inclined surface downwardly inclined from the land part, and an upper surface bottom part extending from the inclined surface,

the land part includes a main cutting edge land part adjacent to the main cutting edge, a nose R part land part connected to the main cutting edge land part and adjacent to the nose R part, and a sub-cutting edge land part connected to the nose R part land part and adjacent to the sub-cutting edge,

the inclined surface includes a main cutting edge inclined surface downwardly inclined from the main cutting edge land part, a nose R part inclined surface connected to the main cutting edge inclined surface and downwardly inclined from the nose R part land part, and a sub-cutting edge inclined surface connected to the nose R part inclined surface and downwardly inclined from the sub-cutting edge land part, and

first and second protrusion parts are formed respectively, wherein the first protrusion part is connected to the main cutting edge land part and formed on the main cutting edge inclined surface at a portion at which the nose R part inclined surface ends, and the second protrusion part is connected to the sub-cutting edge land part and formed on the sub-cutting edge inclined surface at a portion at which the nose R part inclined surface ends, and no protrusion is present on the nose R part inclined surface.

2 . The cutting insert of claim 1 , wherein the first protrusion part and the second protrusion part have the same height as that of the main cutting edge land part and the sub-cutting edge land part.

3 . The cutting insert of claim 1 , wherein a plurality of troughs and a plurality of crests are alternately connected with each other on the upper surface bottom part, and

the plurality of crests is sequentially lowered in height and at a smaller angle with a horizontal plane as being farther away from the sub-cutting edge.

4 . The cutting insert of claim 3 , wherein each of the plurality of crests has a gradually increasing height as going from the main cutting edge toward the fastening hole.

5 . The cutting insert of claim 1 , wherein the upper surface bottom part includes a nose R part bottom part connected to the nose R part inclined surface, and a cutting edge part bottom part including the plurality of troughs and the plurality of crests formed therein, and

the nose R part bottom part is formed to be higher than the plurality of crests.

6 . The cutting insert of claim 5 , wherein the nose R part bottom part includes a first concave groove, and each of the plurality of crests includes a second concave groove at its end, and

a radius of curvature of the first concave groove is greater than that of the second concave groove.

7 . The cutting insert of claim 3 , wherein the plurality of troughs has a greater width as being closer to the main cutting edge, and

the plurality of troughs has a greater size of a relative width as being farther away from the nose R part.

8 . The cutting insert of claim 1 , comprising a boss part surrounding the fastening hole, wherein

the boss part includes a groove part having one end facing toward the sub-cutting edge and the other end facing toward the main cutting edge.

9 . A cutting tool on which the cutting insert of claim 1 is mounted.