An apparatus for assembling teeth (d) that constitute the stator poles of a stator comprising a supporting structure provided with at least one seat for accommodating teeth (d) during assembly, said seat having a central axis, further comprising: - a radial expansion device, which is arranged at said central axis and is configured to expand radially with respect to said central axis, - a plurality of radial compression devices, which are arranged substantially radially around said radial expansion device and are configured to expand radially toward said central axis; said radial expansion device and said radial compression devices forming between them a cavity that is adapted to accommodate said teeth (d) during assembly so that the radial expansion of said radial expansion device pushes each tooth (d) so as to move radially away from said central axis and the expansion of said radial compression devices pushes radially said teeth (d) toward said central axis, the expansion of said radial expansion device and the expansion of said radial compression devices being controlled by at least one electronic control unit, characterised in that, each radial compression device is configured to push a single tooth (d) and comprises: a force detection device for measuring the thrust that said radial compression device applies to said single tooth (d), a position detection device for detecting the radial distance of said tooth (d) from said central axis; said electronic control unit being configured to control the expansion of said radial expansion device and the expansion of said radial compression devices as a function of the values detected by said position detection device and by said force detection device, and each one of said radial compression devices comprising a drive unit which, by means of a kinematic chain, induces the radial movement, with respect to said central axis, of a pusher head which is configured to push radially said tooth (d) toward said central axis; said drive unit being controlled by said electronic control unit, said kinematic chain comprising a pusher shaft which is actuated by said drive unit and is functionally connected to a pusher wedge in order to actuate the linear movement of the latter along a direction that is parallel to said central axis, said pusher wedge being connected kinematically to said pusher head so that by moving along said linear direction it imparts to said pusher head a radial thrust toward said central axis; said force detection device being interposed between said pusher shaft and said pusher wedge, said position detection device being configured to detect the position of said pusher head, said pusher wedge being connected to said pusher head by means of a transmission cylinder and an intermediate transmission element which kinematically connects said transmission cylinder to said pusher head. - a radial expansion device, which is arranged at said central axis and is configured to expand radially with respect to said central axis, - a plurality of radial compression devices, which are arranged substantially radially around said radial expansion device and are configured to expand radially toward said central axis; said radial expansion device and said radial compression devices forming between them a cavity that is adapted to accommodate said teeth (d) during assembly so that the radial expansion of said radial expansion device pushes each tooth (d) so as to move radially away from said central axis and the expansion of said radial compression devices pushes radially said teeth (d) toward said central axis, the expansion of said radial expansion device and the expansion of said radial compression devices being controlled by at least one electronic control unit, characterised in that, said radial expansion device and said radial compression devices forming between them a cavity that is adapted to accommodate said teeth (d) during assembly so that the radial expansion of said radial expansion device pushes each tooth (d) so as to move radially away from said central axis and the expansion of said radial compression devices pushes radially said teeth (d) toward said central axis, the expansion of said radial expansion device and the expansion of said radial compression devices being controlled by at least one electronic control unit, characterised in that,