Throw-away tip

1. A throw-away tip comprising a body and a blade provided to the body and having a cutting edge,

the blade containing 80% by volume or more of diamond,

the blade having a land surface extending along the cutting edge, and a chip breaker having a recess located opposite to the cutting edge with the land surface therebetween,

the recess having a side surface having a rake face that recedes continuously from the land surface as a distance toward a center of the blade increases in magnitude, wherein

the rake face has a shape identical to a portion of a side surface of a cone;

the blade has a corner;

the recess has on the side surface of the recess a projection formed along a bisector of an angle of the corner;

the projection has a height in a range of 20% or more and 80% or less relative to a maximum depth of the recess;

the maximum depth of the recess is a maximum value of a distance to a bottom of the recess from a plane assumed when the land surface is extended to above the recess; and

the cone has an axis on the bisector of the angle of the corner of the blade.

2. The throw-away tip according to claim 1 , wherein an angle of inclination of the rake face relative to the land surface is in a range of 15° or more and 50° or less.

3. The throw-away tip according to claim 1 , wherein the land surface has a width in a direction perpendicular to the cutting edge in a range of 10 μm or more and 100 μm or less.

4. The throw-away tip according to claim 1 , wherein the recess has a maximum depth in a range of 60 μm or more and 300 μm or less.

5. The throw-away tip according to claim 1 , wherein the recess has a width in a direction perpendicular to the cutting edge in a range of 0.2 mm or more and 1.0 mm or less.

6. The throw-away tip according to claim 1 , wherein when the projection is seen in a cross section to which the bisector of the angle of the corner is a normal, the projection has a cross sectional shape increasing in width as the recess becomes deeper; and

the cross sectional shape in a widthwise direction has a minimum value in a range of 5 μm or more and 40 μm or less.

7. The throw-away tip according to claim 1 , wherein the projection has a length in a direction along the bisector of the angle of the corner in a range of 0.2 mm or more and 1.0 mm or less.

8. The throw-away tip according to claim 1 , wherein:

the land surface has a surface roughness in a range of 0.05 μm or more and 0.2 μm or less; and

the rake face has a surface roughness in a range of 2 μm or more and 7 μm or less.

9. The throw-away tip according to claim 1 , wherein the diamond is single crystal diamond synthesized by vapor deposition.

10. The throw-away tip according to claim 9 , wherein the single crystal diamond has an absorption coefficient in a range of 2 cm −1 or more and 90 cm −1 or less for laser light of 190 μm or more and 11000 μm or less in wavelength.

11. The throw-away tip according to claim 1 , wherein the land surface, the rake face, the projection, a breaker wall surface, and an upper surface are arranged in order along the bisector,

and

wherein a width of the rake face along the bisector is larger than a width of the breaker wall surface along the bisector.

12. The throw-away tip according to claim 1 , wherein the land surface, the rake face, the projection, a breaker wall surface, and an upper surface are arranged in order along the bisector,

and

wherein a width of the rake face and the breaker wall surface along the bisector is greater than a width of the land surface along the bisector.

13. The throw-away tip according to claim 1 , wherein the rake face is linear along the bisector.