A rotary tool is specified, comprising a cutting insert and a clamping holder extending in an axial direction wherein the clamping holder has a lateral surface extending in the axial direction, wherein the cutting insert has at least one cutting portion for machining a workpiece, and a fastening portion which is connected to the cutting portion, wherein the fastening portion has a fastening surface with which the cutting insert is detachably fastened to the lateral surface by means of a fastener, wherein the clamping holder has a support projection and a support, which each extend away from the lateral surface, wherein the fastening portion has a fastening portion upper side and a fastening portion lower side each of which is designed in a stepped manner in the axial direction, wherein an upper side partial surface of the fastening portion upper side abuts against a support projection surface of the support projection and a lower side partial surface of the fastening portion lower side abuts against the support. A cutting insert and a clamping holder are also specified.