A mixing shaft has a tool holder rotatable about a tool axis and at least one mixing blade. The tool holder includes at least one recess in which a mixing blade portion of the at least one mixing blade is received. A clamping member inserted into the recess is configured to fix the mixing blade portion in the recess. The recess includes a first and a second recess portion. The mixing blade portion is arranged in the first recess portion and the clamping member is arranged at least partly in the second recess portion, wherein the first recess portion and the second recess portion are arranged adjacently in one plane extending perpendicularly to the tool axis.