a method of assembling a dynamoelectric machine is disclosed in which a rotor tool is inserted into the stator bore with the tool having an outer diameter substantially equal to or slightly less than the minimum allowable inner diameter of the stator bore . the tool further has a central pin which is inserted into the bearing bore of the motor bearing support or end shield . portions of the end shield are disposed on the outside of the stator core when the end shield and the stator core are in their desired assembled positions . then , these portions of the end shield are magnetically deformed inwardly , as by magnetic pulse forming or the like , for positively securing the end shield to the stator core such that the rotor tool maintains alignment of the bearing bore with respect to the stator bore . the rotor tool is removed , and the rotor is inserted in the stator core and in the bearing bore of the end shield such that an air gap of predetermined uniform thickness is established and maintained between the rotor body and the stator core . apparatus for carrying out the above - described method is also disclosed .