A device for mechanically cleaning a grooves used to hold a rotor or a stator winding of an electric machine includes an axially moveable device carrier and at least one cleaning tool connected to the device carrier and extending radially from the device carrier into the groove. In addition, a corresponding method includes the steps of radially moving at least one cleaning tool connected to a device carrier so as to mechanically remove impurities on a wall section of the groove, axial advancing of the device carrier in a manner adapted to the radial movement of the at least one cleaning tool, and setting the dimensional tolerance range for the groove by adjusting the cleaning tool. The device and the method are suitable for cleaning grooves into which a new winding is to be installed in an existing laminated body, for example, in the case of the retrofitting of generators.