Abstract: A machine tool includes a table, a spindle head, a spindle, and an internal turning attachment. The internal turning attachment includes an attachment base, a body, and a tool holder. The tool holder has a tool mount surface to which a turning tool is detachably mounted. The tool mount surface provides a changeable tool mount angle with respect to a plane perpendicular to a spindle rotational axis in a state where the internal turning attachment is mounted to the spindle head. An angle between the spindle rotational axis and a vertical axis is to be larger than zero degree according to the changeable tool mount angle and is fixed while the turning tool contacts a workpiece in a case where the workpiece has a hole with a depth exceeding a length from a body upper portion to a tip end of the turning tool along the spindle rotational axis.

Abstract: A machine tool includes a table, a spindle head, a spindle, and an internal turning attachment. The internal turning attachment includes an attachment base, a body, and a tool holder. The tool holder has a tool mount surface to which a turning tool is detachably mounted. The tool mount surface provides a changeable tool mount angle with respect to a plane perpendicular to a spindle rotational axis in a state where the internal turning attachment is mounted to the spindle head. An angle between the spindle rotational axis and a vertical axis is to be larger than zero degree according to the changeable tool mount angle and is fixed while the turning tool contacts a workpiece in a case where the workpiece has a hole with a depth exceeding a length from a body upper portion to a tip end of the turning tool along the spindle rotational axis.