The present disclosure relates to methods and tools for mounting and/or removing active parts of a stator of an electrical machine, e.g. a generator. The present disclosure also relates to rotors, stators and generators. A method comprises removing one or more active rotor parts of a rotor of an electrical machine when the rotor is in a removal starting position, arranging a replacement tool in a gap left by the removed active rotor parts, rotating the rotor to an alignment position such that the replacement tool is radially aligned with an active stator part to be removed, picking the active stator part to be removed with the replacement tool, rotating the rotor to an extraction position, and removing the active stator part from the rotor.