The present invention relates to an auxiliary tool for assembling a scrubber which includes a motor, a shaft rotatably coupled to and extending through the motor, a shaft pin detachably connected to the shaft, and a disk coupled to the shaft and having a notch located relative to the shaft pin at a predetermined angle with respect to a longitudinal axis of the shaft when properly assembled. In specific embodiments, the auxiliary tool comprises a tool body configured to at least partially receive the motor, the shaft pin, the disk, and the notch of the disk. The tool body includes a first recess configured to at least partially receive the shaft pin and a protrusion configured to be at least partially received into the notch of the disk. The first recess and the protrusion are arranged at the predetermined angle to position the notch of the disk and the shaft pin of the scrubber for proper assembly at the predetermined angle with respect to the longitudinal axis of the shaft.