In order to facilitate the automated assembly of an electric motor, all of the major components and sub-assemblies thereof are successively brought together in one axial direction. Such major components of the motor include a first cylindrical case, preferably of aluminum, having an end wall at only one end so as to slidably receive, through its other open end, a second magnetic cylindrical case which is relatively shorter than the first case and which opens in the same axial direction for receiving and housing a cylindrical magnet, a rotor assembly insertable through the open end of the second case and including a shaft with a rotor and commutator thereon, a brush base insertable in the open end of the first case so as to bear against the open end edge of the second case and carrying brushes at one side to engage the commutator and a frequency generator at its other side, and a lid member carrying a central thrust bearing for engagement by the respective end of the shaft when the lid member is engaged with the open end of the first case for closing the latter and for bearing against the frequency generator.