Abstract: When seen in a direction perpendicular to a seating surface, the second boundary line has a first portion and a second portion, the first portion having an inclination relative to the second cutting edge portion in a counter clockwise direction, the first portion being located between the first boundary line and an intersection between the second boundary line and a straight line passing through a center of a mounting hole and perpendicular to the second cutting edge portion, the second portion being located opposite to the first portion relative to the intersection, the second portion having an inclination relative to the second cutting edge portion in a clockwise direction.

Abstract: When seen in a direction perpendicular to a seating surface, the second boundary line has a first portion and a second portion, the first portion having an inclination relative to the second cutting edge portion in a counter clockwise direction, the first portion being located between the first boundary line and an intersection between the second boundary line and a straight line passing through a center of a mounting hole and perpendicular to the second cutting edge portion, the second portion being located opposite to the first portion relative to the intersection, the second portion having an inclination relative to the second cutting edge portion in a clockwise direction.

Abstract: A rotary cutting tool insert according to one embodiment of the present invention includes: an annular rake face provided with at least one recess portion; and a cutting edge formed at an outer circumference of the rake face, the recess portion having a width of more than or equal to 1.2 mm and less than or equal to 3.0 mm in a circumferential direction of the rake face, a distance between the cutting edge and an end of the recess portion at the outer circumference side of the rake face being more than or equal to 0.1 mm and less than or equal to 0.5 mm. According to the rotary cutting tool insert according to the one embodiment of the present invention, roughness of a processed surface and vibration due to a cutting process can be prevented.

Abstract: A cutting insert includes a leading cutting edge having a rake angle in the range of 20° to 35° in a central region in a width direction; and a rake face having a breaker groove formed in the central region in the width direction and land portions formed in both end regions in the width direction. The land portions have a rake angle smaller than the rake angle in the central region in the width direction. The breaker groove includes opposing side faces separated from each other by a distance that decreases with increasing distance from the leading cutting edge and four shoulder portions of the same height that are formed on the opposing side faces at positions above the land portions, two of the shoulder portions being closer to the leading cutting edge and to outer sides in the width direction than the other two shoulder portions are.

Abstract: A rotary cutting tool insert according to one embodiment of the present invention includes: an annular rake face provided with at least one recess portion; and a cutting edge formed at an outer circumference of the rake face, the recess portion having a width of more than or equal to 1.2 mm and less than or equal to 3.0 mm in a circumferential direction of the rake face, a distance between the cutting edge and an end of the recess portion at the outer circumference side of the rake face being more than or equal to 0.1 mm and less than or equal to 0.5 mm. According to the rotary cutting tool insert according to the one embodiment of the present invention, roughness of a processed surface and vibration due to a cutting process can be prevented.

Abstract: A cutting insert is configured to include: a first portion having a rake face, a flank face, a cutting edge, and a face facing an insert attachment portion at an end of a tool main body; and a second portion having a side surface including at least one flat plane that is parallel to a center line of a tool or inclined at a prescribed angle to the center line. The second portion extends continuously to a region surrounded by the face of the first portion. The second portion is fitted into the tool main body to position the cutting insert and to prevent the cutting insert from rotating.

Abstract: A cutting insert includes a leading cutting edge having a rake angle in the range of 20° to 35° in a central region in a width direction; and a rake face having a breaker groove formed in the central region in the width direction and land portions formed in both end regions in the width direction. The land portions have a rake angle smaller than the rake angle in the central region in the width direction. The breaker groove includes opposing side faces separated from each other by a distance that decreases with increasing distance from the leading cutting edge and four shoulder portions of the same height that are formed on the opposing side faces at positions above the land portions, two of the shoulder portions being closer to the leading cutting edge and to outer sides in the width direction than the other two shoulder portions are.

Abstract: A cutting insert is configured to include: a first portion having a rake face, a flank face, a cutting edge, and a face facing an insert attachment portion at an end of a tool main body; and a second portion having a side surface including at least one flat plane that is parallel to a center line of a tool or inclined at a prescribed angle to the center line. The second portion extends continuously to a region surrounded by the face of the first portion. The second portion is fitted into the tool main body to position the cutting insert and to prevent the cutting insert from rotating.