Abstract: Provided is a structure for improving accuracy in attaching a cutting tool to a body and making it possible to increase the number of blades while the cutting tool is mounted on the body. A cutting insert 1 includes: an upper surface 10 that has a shape with a lengthwise direction LD and a widthwise direction SD; a lower surface that is located opposite to the upper surface 10; a peripheral side surface 30 that is formed so as to connect the upper surface 10 and the lower surface; cutting edges 51 and 52 that are respectively formed on an intersecting ridge line of the upper surface 10 and the peripheral side surface 30, and on an intersecting ridge line of the lower surface and the peripheral side surface 30, and each have a curved ridge line that extends in a lengthwise direction thereof; and a through hole 60 that penetrates from the upper surface 10 to the lower surface.

Abstract: Provided is a cutting tool capable of improving both the biting property to a work material and the chip discharge property. The cutting tool includes a drill body rotated about a central axis, four or more cutting edges formed on one end portion of the drill body to face a forward side of a rotation direction, and a flute groove that is formed between the cutting edges adjacent to each other in a circumferential direction and extends substantially spirally along the central axis.

Abstract: Provided is a structure for improving accuracy in attaching a cutting tool to a body and making it possible to increase the number of blades while the cutting tool is mounted on the body. A cutting insert 1 includes: an upper surface 10 that has a shape with a lengthwise direction LD and a widthwise direction SD; a lower surface that is located opposite to the upper surface 10; a peripheral side surface 30 that is formed so as to connect the upper surface 10 and the lower surface; cutting edges 51 and 52 that are respectively formed on an intersecting ridge line of the upper surface 10 and the peripheral side surface 30, and on an intersecting ridge line of the lower surface and the peripheral side surface 30, and each have a curved ridge line that extends in a lengthwise direction thereof; and a through hole 60 that penetrates from the upper surface 10 to the lower surface.

Abstract: Provided is a structure for improving accuracy in attaching a cutting tool to a body and making it possible to increase the number of blades while the cutting tool is mounted on the body. A cutting insert 1 includes: an upper surface 10 that has a shape with a lengthwise direction LD and a widthwise direction SD; a lower surface that is located opposite to the upper surface 10; a peripheral side surface 30 that is formed so as to connect the upper surface 10 and the lower surface; cutting edges 51 and 52 that are respectively formed on an intersecting ridge line of the upper surface 10 and the peripheral side surface 30, and on an intersecting ridge line of the lower surface and the peripheral side surface 30, and each have a curved ridge line that extends in a lengthwise direction thereof; and a through hole 60 that penetrates from the upper surface 10 to the lower surface.

Abstract: Provided is a cutting tool capable of improving both the biting property to a work material and the chip discharge property. The cutting tool includes a drill body rotated about a central axis, four or more cutting edges formed on one end portion of the drill body to face a forward side of a rotation direction, and a flute groove that is formed between the cutting edges adjacent to each other in a circumferential direction and extends substantially spirally along the central axis.