Drill and method for manufacturing machined product
A drill may include a base. The base may be extended from a first end to a second end. The base may include a first part, a second part, a step, a first cutting edge, a first flute, a second cutting edge and a second flute. The step may be located between the first part and the second part, and may have a larger outer diameter as coming closer to the second part. The first flute may be extended from the first cutting edge. The second flute may be extended from the second cutting edge. The step may include a first step and a second step. The first step may connect to the first flute. The second step may connect to the second flute. A first end part in the first step may be located further away from the first end than a second end part in the second step.
1 . A drill, comprising:
a base extended along a rotation axis from a first end to a second end and being rotatable around the rotation axis, and being configured to perform a cutting process when rotated in a rotation direction around the rotation axis, the base comprising:
a first part including the first end and having a first outer diameter,
wherein the first part includes a first cutting edge extending from the first end,
a first flute that leads the first cutting edge relative to the rotation direction,
a second flute that follows the first cutting edge relative to the rotation direction,
a second part which is between the first cutting edge and the second end, and has a second outer diameter that is larger than the first outer diameter,
a step which is located between the first cutting edge and the second part and has a larger outer diameter as coming closer to the second part,
wherein:
a length of each of the first part and the second part is longer than a length of the step,
the step comprises:
a first step that is a non-cutting step, and
a second step that includes a second cutting edge such that the second step is a cutting step,
each of the first and second steps is located where the first outer diameter increases to the second outer diameter,
the second step is between the first cutting edge and the first step,
the second flute is between the first step and the second step relative to the rotation direction,
the first step leads second flute relative to the rotation direction, and
the second step follows the second flute relative to the rotation direction.
2 . The drill according to claim 1 , wherein a length from a first end part of the first step to a second end part of the second step is larger than a length of the second cutting edge in a direction along the rotation axis.
3 . The drill according to claim 1 , wherein a first imaginary straight line connecting an end part on a side of an outer periphery in the first cutting edge and the rotation axis is orthogonal to a second imaginary straight line connecting an end part on a side of the outer periphery in the second cutting edge and the rotation axis in a plan view from a side of the first end.
4 . The drill according to claim 1 , wherein
an outer peripheral surface of the second part comprises
a first portion connecting to the first flute on a rear side in the rotation direction, and
a second portion connecting to the second flute on a rear side in the rotation direction, and
a width of the first portion is larger than a width of the second portion in a cross section orthogonal to the rotation axis.
5 . The drill according to claim 4 , wherein
the first portion comprises a first margin,
the second portion comprises a second margin, and
a width of the second margin is larger than a width of the first margin in the cross section.
6 . The drill according to claim 5 , wherein
the first portion further comprises a first clearance connecting to the first margin on a rear side in the rotation direction,
the second portion further comprises a second clearance connecting to the second margin on a rear side in the rotation direction, and
a width of the first clearance is larger than a width of the second clearance in the cross section.
7 . A method for manufacturing a machined product, comprising:
rotating the drill according to claim 1 ;
bringing the drill being rotated into contact with a workpiece; and
moving the drill away from the workpiece.
8 . The drill according to claim 1 , wherein
the first flute and the second flute are spiral.
9 . The drill according to claim 1 , wherein
a width of the first flute is larger than a width of the second flute.