Cutting insert and method for manufacturing cutting insert

1. A cutting insert comprising: a rake face; a flank face continuous to the rake face; and a cutting edge constituted of a ridgeline between the rake face and the flank face, wherein

a coolant flow path is provided inside the cutting insert,

one end portion of the coolant flow path opens in the flank face to form a coolant ejection hole,

the flank face is provided with a coolant guide groove extending from the coolant ejection hole toward the cutting edge with a base end portion of the coolant guide groove being connected to the coolant ejection hole and with a front end portion of the coolant guide groove being disposed at a position close to the cutting edge relative to the base end portion,

the coolant flow path is inclined such that a distance between the coolant flow path and the cutting edge becomes smaller as the coolant flow path is closer to the flank face,

the cutting insert is constituted of a cutting edge tip composed of cubic boron nitride and a substrate composed of cemented carbide,

the cutting edge tip is attached to the substrate,

the coolant ejection hole is at the flank face which is located at the substrate, and

the coolant guide groove extends into the flank face of the cutting edge tip.

2. The cutting insert according to claim 1 , wherein a cross sectional area of the coolant guide groove in a cross section parallel to the rake face becomes smaller from the base end portion toward the front end portion.

3. The cutting insert according to claim 2 , wherein

the cross sectional area is an area of a portion surrounded, in the cross section parallel to the rake face, by a wall surface of the coolant guide groove and a straight line that connects both ends of the coolant guide groove.

4. The cutting insert according to claim 1 , wherein the coolant guide groove has a depth of more than or equal to 0.2 mm and less than or equal to 2 mm.

5. The cutting insert according to claim 1 , wherein

the coolant guide groove has a curved cross sectional shape in a cross section parallel to the rake face.

6. The cutting insert according to claim 1 , wherein

the coolant guide groove has a rectangular cross sectional shape in a cross section parallel to the rake face.

7. The cutting insert according to claim 1 , wherein

the coolant guide groove has a first end and a second end,

the first end is an end of the coolant guide groove at a side of the cutting edge,

the second end is an end of the coolant guide groove at a side of the coolant flow path, and

a distance between the cutting edge and the first end in a direction orthogonal to the cutting edge is equal to or more than 0.3 mm and less than or equal to 1.5 mm.

8. A method for manufacturing the cutting insert recited in claim 1 , the method comprising:

preparing a shaped body for the cutting insert;

forming the rake face, the flank face, and the cutting edge in the shaped body;

forming the coolant flow path inside the shaped body and forming the coolant ejection hole in the flank face; and

forming the coolant guide groove in the flank face.