The winder shaft for a sewing machine, fashioned as a support for a thread bobbin, is positioned directly on the shaft of a low-voltage motor, independent of the drive motor for the sewing mechanism of the sewing machine. An on/off switch for this motor is operable by means of a three-armed switching lever, with the first arm being adapted to scan the package of wound thread forming on the bobbin. A trigger cam disposed on the third arm slides, during this operation, over a first surface of a spring-biased dual ramp. Once the thread bobbin is full, the trigger cam surpasses the apex of the dual ramp, and the switching lever flips into a disconnect position and cuts off the motor by way of a switching cam disposed on the second arm. All of the elements of the spooling device are mounted to a common support so that the spooling device, which is independent of the drive mechanism of the sewing machine, can be attached as a composite unit at any desired location on the sewing machine.