A rotary tool according to a non-limiting aspect includes a body having a rotation axis and extending from a first end to a second end. The body including: a first part including the first end; a second part located closer to a second end than the first part and having a larger outside diameter than the first part; a cutting edge located at a side of the first end; a ridge portion located in the first part and the second part, connected to the cutting edge and helically extending from the cutting edge toward the second end; and a flute located along the ridge portion. The flute includes: a first flute located at the first part and having a first helix angle; and a second flute located at the second part and having a second helix angle. The second helix angle is smaller than the first helix angle.

Provided is a taper reamer with which it is possible to achieve an improvement in machining accuracy and machining life. The taper reamer comprises a plurality of cutting edges each having a helical shape provided on the outer periphery of a cutting-edge portion having an external diameter being expanded from a front end toward a rear end thereof, wherein an intertooth angle, defined between each of a pair of the cutting edges adjacently arranged in a circumferential direction, is different from one another at any given reference position, and wherein the plurality of cutting edges each have a helix angle that is different from one another. As the plurality of cutting edges that are unequally partitioned each have the helix angle that is different from one another, a resonance during cutting can be prevented.

A rotary tool may include a body, the body may include a cutting edge and a first groove. The first groove may include a first region having a first helix angle, a second region having a second helix angle, a third region having a third helix angle, a fourth region having a fourth helix angle, and a fifth region having a fifth helix angle. The fourth helix angle and the fifth helix angle may each decrease from a side of a first end toward a second end. A decreasing range of a value of the fourth helix angle of the fourth region may be less than a decreasing range of a value of the fifth helix angle of the fifth region. A length of the fourth region may be greater than a length of the fifth region.

Provided is a taper reamer with which it is possible to achieve an improvement in machining accuracy and machining life. The taper reamer comprises a plurality of cutting edges each having a helical shape provided on the outer periphery of a cutting-edge portion having an external diameter being expanded from a front end toward a rear end thereof, wherein an intertooth angle, defined between each of a pair of the cutting edges adjacently arranged in a circumferential direction, is different from one another at any given reference position, and wherein the plurality of cutting edges each have a helix angle that is different from one another. As the plurality of cutting edges that are unequally partitioned each have the helix angle that is different from one another, a resonance during cutting can be prevented.

A rotary tool according to a non-limiting aspect includes a body having a rotation axis and extending from a first end to a second end. The body including: a first part including the first end; a second part located closer to a second end than the first part and having a larger outside diameter than the first part; a cutting edge located at a side of the first end; a ridge portion located in the first part and the second part, connected to the cutting edge and helically extending from the cutting edge toward the second end; and a flute located along the ridge portion. The flute includes: a first flute located at the first part and having a first helix angle; and a second flute located at the second part and having a second helix angle. The second helix angle is smaller than the first helix angle.

A rotary tool may include a body, the body may include a cutting edge and a first groove. The first groove may include a first region having a first helix angle, a second region having a second helix angle, a third region having a third helix angle, a fourth region having a fourth helix angle, and a fifth region having a fifth helix angle. The fourth helix angle and the fifth helix angle may each decrease from a side of a first end toward a second end. A decreasing range of a value of the fourth helix angle of the fourth region may be less than a decreasing range of a value of the fifth helix angle of the fifth region. A length of the fourth region may be greater than a length of the fifth region.