Cutting insert, rotary tool, and method for manufacturing machined product

A cutting insert for use in a rotary tool rotatable about a rotation axis, the cutting insert comprising:

• a base portion comprising:
• a first rear surface located rearward in a rotation direction of the rotary tool;
• a first front surface located on an outer side in a radial direction and facing forward in the rotation direction;
• and
• a first end surface located on a front end side in a direction along the rotation axis, and being connected to the first rear surface and the first front surface;
• and
• a cutting portion comprising:
• a second rear surface that is flat and is bonded to the first front surface;
• a second front surface that is flat and is located opposite to the second rear surface;
• a second end surface located on the front end side and being connected to the second rear surface and the second front surface;
• and
• a cutting edge located at an intersection of the second front surface and the second end surface, wherein,
• when viewed from the front end side,
• the first end surface comprises:
• a first region located rearward of the second rear surface in the rotation direction and being located to the outer side in the radial direction;
• and
• a second region located rearward of the second front surface in the rotation direction and being located further to an inner side in the radial direction than the first region, and
• when a virtual plane including the second rear surface is a reference plane,
• the first region comprises a first portion in which a width of a region interposed between the reference plane and the first rear surface gradually increases toward the outer side in the radial direction due to a curved shape of the first rear surface, and
• the second region comprises a second portion in which a width of a region interposed between the reference plane and the first rear surface gradually increases toward the inner side in the radial direction.