Corner radius end mill

1. A corner radius end mill configured for rotating about a rotation axis (A R ), comprising:

a shank portion; and

a cutting portion extending from the shank portion and having a diameter (D);

the cutting portion comprising:

a helical flute having a helix angle H which fulfills the condition 20°<H<60° and comprising a flute rake surface;

a cutting tooth comprising a cutting edge which extends adjacent to the flute rake surface, and comprising a corner sector with a corner radius R which fulfills the condition R>0.15 D, a first half-sector of the corner sector extending from an imaginary bisection line of the corner sector to a radial tangent point and a second half-sector of the corner sector extending from the imaginary bisection line to an axial tangent point, the first and second half-sectors subtending equal angles about the imaginary bisection line;

an end gash surface extending adjacent the cutting edge and the flute rake surface; and

a blended gash extending along the cutting edge from a first extremity located in the second half-sector in a direction away from the first half-sector, and blending the end gash surface and the flute rake surface.

2. The corner radius end mill according to claim 1 , wherein the second half-sector comprises a traverse sub-sector having a traverse central angle, the traverse sub-sector being distally located from the first half-sector, and wherein the blended gash extends into the second half-sector traversing the traverse sub-sector.

3. The corner radius end mill according to claim 2 , wherein the traverse central angle is 10°.

4. The corner radius end mill according to claim 2 , wherein the traverse central angle is 25°.

5. The corner radius end mill according to claim 1 , wherein the second half-sector comprises a boundary sub-sector having a boundary central angle, the boundary sub-sector extending from the imaginary bisection line, and wherein the blended gash does not extend into the boundary sub-sector.

6. The corner radius end mill according claim 5 , wherein the boundary central angle is 1°.

7. The corner radius end mill according to claim 5 , wherein the boundary central angle is 2°.

8. The corner radius end mill according to claim 1 , wherein a discontinuity formed at an intersection of the cutting edge, blended gash and flute rake surface is located at said axial side.

9. The corner radius end mill according to claim 8 , wherein the discontinuity forms at least a 1° discontinuity angle.

10. The corner radius end mill according to claim 8 , wherein the discontinuity forms at most a 10° discontinuity angle.

11. The corner radius end mill according to claim 1 , wherein a radial rake angle along an entirety of a radial portion of the cutting edge has positive values.

12. The corner radius end mill according to claim 11 , wherein all values of the radial rake angle is equal to or greater than 5°.

13. The corner radius end mill according to claim 1 , being configured for cutting workpiece materials having a Rockwell's hardness less than 42 HRc.

14. The corner radius end mill according to claim 1 , further comprising at least one additional helical flute and associated cutting tooth comprising a blended gash.

15. The corner radius end mill according to claim 1 , wherein the helix angle H fulfills the condition 35°≦H≦45°.

16. The corner radius end mill according to claim 1 , wherein, at a cutting end face, at least one index angle has a value different to at least one other index angle thereof.

17. The corner radius end mill according to claim 1 , wherein, at a cutting end face, all index angles have different values.

18. The corner radius end mill according to claim 1 , wherein at an equal-index-angle plane (P E ) perpendicular to a rotation axis (A R ), the corner radius end mill has all of the index angles thereof being equal.

19. The corner radius end mill according to claim 18 , wherein said equal-index-angle plane (P E ) is located in the middle of an active cutting portion of the cutting portion.

20. The corner radius end mill according to claim 1 , wherein a non-gashed corner area of the corner sector at the cutting edge, which is closer than the blended gash to the radial tangent point, has a rake angle at least 5° greater than a rake angle of the blended gash at the cutting edge.