Patent ID: 11865626
Assignee: OSG CORPORATION
Field: Machine tools (Mechanical engineering)
Classification: CPC B | IPC B

Claim 0:
1. A drill comprising:
a body configured to extend along a shaft center;
a plurality of discharge grooves provided in a helical shape in an outer peripheral surface of the body from a leading end portion of the body toward a base end portion of the body wherein each of the discharge grooves is configured with two inner surfaces, one of which being a first inner surface facing a rotation direction of the body and the other of which being a second inner surface facing an opposite direction to the rotation direction;
a cutting edge provided on a ridge section between the first inner surface of the discharge groove and a flank on the leading end portion of the body;
a thinning edge configured to extend from an inner end of the cutting edge, in a radial direction of the body, toward an inner side in the radial direction; and
a gash portion provided on the second inner surface and including a curved portion in which a first ridge line between the second inner surface and the flank extends while curving toward the rotation direction, from an inner end of the thinning edge toward an outer side in the radial direction, and a straight portion in which a second ridge line between the second inner surface and the flank extends linearly from an outer end of the first ridge line in the radial direction toward the outer side in the radial direction, the second ridge line being configured to connect to the discharge groove further to the inner side in the radial direction than the outer peripheral surface of the body, wherein
a marginal portion is further provided adjacent to the straight portion at the outer side in the radial direction on the second inner surface, having a marginal ridge line that is formed between the flank and the second inner surface wherein the marginal ridge line is continuous to an outer end of the second ridge line and connected to a heel of the flank and the heel is a trailing edge of the outer peripheral surface corresponding to the flank in the rotation direction,
the marginal portion faces a different direction than the straight portion,
as seen from an axial direction in which the shaft center extends, the marginal ridge line is positioned at a predetermined angle, of which a value is positive, with respect to an imaginary extension of the second ridge line in the rotation direction, and
an arc length of the first ridge line is greater than a linear length of the second ridge line.