Patent ID: 11872641
Assignee: KYOCERA CORPORATION
Field: Machine tools (Mechanical engineering)
Classification: CPC B | IPC B

Claim 10:
11. A drill, comprising:
a main body having a bar shape extending from a first end to a second end, the main body configured to rotate around a rotation axis, and comprising:
a cutting edge located at a side of the first end,
a first flute extending from the cutting edge toward the second end, and
a second flute extending from the first flute toward the second end,

wherein, the first flute comprises a chip formation surface configured to smoothly curl chips, the chip formation surface comprising, in a first cross section orthogonal to the rotation axis,
a first portion having a concave curvilinear shape located at a more rear side of the first flute in a rotation direction of the rotation axis than a bottom of the first flute, and
a second portion having a convex curvilinear shape located at a more front side of the first flute in the rotation direction than the bottom of the first flute;
the second flute has a concave curvilinear shape from a front end portion located at a front side of the second flute in the rotation direction to a rear end portion located at a rear side of the second flute in the rotation direction in a second cross section
orthogonal to the rotation axis; and
the second portion comprises:
a first region located at a side of the first end, and
a second region located closer to the second end than the first region; and
a length of the second portion along the convex curvilinear shape of the second portion in the first cross section orthogonal to the rotation axis in the first region is shorter than a length of the second portion along the convex curvilinear shape of the second portion in a third cross section orthogonal to the rotation axis in the second region.