Drill

1. A drill comprising:

a rake face;

a flank face continuous to the rake face; and

an outer circumferential surface continuous to both the rake face and the flank face, wherein

a ridgeline between the rake face and the flank face constitutes a cutting edge,

a ridgeline between the rake face and the outer circumferential surface constitutes an outer circumferential end,

a groove is provided cyclically in the rake face to extend at an angle relative to an axis of the drill, the angle being larger than a helix angle of the drill,

the groove has a depth of more than or equal to 1.5 μm,

the groove is inclined relative to the cutting edge,

the groove has a plurality of groove portions, and

each of the plurality of groove portions is continuous to the cutting edge.

2. The drill according to claim 1 , wherein

the drill has a substrate and a coating film provided on the substrate,

the rake face, the flank face, and the outer circumferential surface are constituted of the coating film, and

the groove is a first groove provided in the rake face formed by the coating film and extending from the cutting edge toward the outer circumferential end, and the first groove has a depth of more than or equal to 1.5 μm.

3. The drill according to claim 2 , wherein a second groove is cyclically provided in the substrate at a location corresponding to the first groove, and the second groove has a depth of more than or equal to 1.5 μm.

4. The drill according to claim 3 , wherein a thickness of the coating film is larger than the depth of the second groove.

5. The drill according to claim 3 , wherein the coating film further includes a thinning face continuous to both the flank face and the rake face, and a third groove is provided in the rake face to extend toward the outer circumferential end from a ridgeline between the thinning face and the rake face.

6. The drill according to claim 4 , wherein the third groove has a depth of more than or equal to 1.5 μm.

7. The drill according to claim 4 , wherein a maximum height roughness of the thinning face is smaller than a maximum height roughness of the rake face.

8. The drill according to claim 2 , wherein

the drill is configured to be rotatable around the axis,

the coating film further includes a flute portion continuous to the rake face and provided in a form of a helix around the axis.

9. The drill according to claim 8 , wherein a value obtained by subtracting the helix angle from the angle of an extending direction of the groove relative to the axis is more than 0° and less than or equal to 15°.

10. The drill according to claim 1 , wherein the rake face has a maximum height roughness of more than or equal to 1.5 μm and less than or equal to 50 μm.

11. The drill according to claim 1 , wherein

a pitch between the plurality of groove portions is more than or equal to 10 μm and less than or equal to 70 μm.

12. The drill according to claim 1 , wherein

the flank face has a cutting-edge treated face and a main flank face portion, the cutting-edge treated face constituting the cutting edge, the main flank face portion being continuous to the cutting-edge treated face, the main flank face portion being inclined relative to the cutting-edge treated face, and

a maximum height roughness of the cutting-edge treated face is smaller than a maximum height roughness of the rake face.

13. The drill according to claim 1 , wherein

the outer circumferential surface has a return face and a main outer circumferential surface portion, the return face constituting the outer circumferential end, the main outer circumferential surface portion being continuous to the return face, the main outer circumferential surface portion being inclined relative to the return face, and

a maximum height roughness of the return face is smaller than a maximum height roughness of the rake face.