Cutting tool

A cutting tool rotatable about a rotation axis, the cutting tool comprising a main body that includes a distal end surface, a side surface continuous to the distal end surface, and a rear end surface that is continuous to the side surface and is located on a side opposite to the distal end surface in a direction along the rotation axis,

• wherein a spiral first groove and a spiral second groove are formed on the side surface of the main body,
• the second groove is adjacent to a rear side in a rotation direction of the main body when viewed from the first groove,
• the first groove has at least four installation surfaces inside the first groove,
• the at least four installation surfaces are used to install a cutting insert,
• the at least four installation surfaces include a first installation surface and a second installation surface that are disposed third or later from the distal end surface side of the main body,
• the first installation surface is located on a most rear end surface side among the at least four installation surfaces,
• the second installation surface is located closer to the distal end surface than the first installation surface,
• the at least four installation surfaces have fixing holes fixing the cutting insert, respectively,
• a center of each of the fixing holes on the at least four installation surfaces is set to a center of each of the at least four installation surfaces, and
• when an intersection of the side surface and a semi-straight line is set to a first start point, the semi-straight line passing through the center of the first installation surface and extending toward an outside of the side surface with the rotation axis as a start point, in a first section that passes through the center of the first installation surface and is perpendicular to the rotation axis,
• when an intersection between a side wall of the second groove on the first groove side and the side surface in the first section is set to a first end point,
• when a length of the side surface of the main body from the first start point to the first end point in the first section is set to a first length,
• when an intersection of the side surface and a semi-straight line is set to a second start point, the semi-straight line passing through the center of the second installation surface and extends toward an outside of the side surface with the rotation axis as a start point, in a second section passing through the center of the second installation surface and perpendicular to the rotation axis,
• when an intersection between a side wall of the second groove on the first groove side and the side surface in the second section is set to a second end point, and
• when a length of the side surface of the main body from the second start point to the second end point in the second section is set to a second length,
• the first length is longer than the second length.