A rotary catheter drive unit containing a motor and a seal-set, an output shaft of the motor being power transmittingly connected to a flexible shaft that is rotatably disposed through the seal-set, the seal-set comprising a bearing and an adjacent seal defining a first and a second concentric bores, respectively, the first bore being slightly larger than a diameter of the shaft so that it rotatably and accurately supports the shaft, the second bore being slightly smaller than the diameter so that it seals around the shaft, the bearing aligning the shaft, so that it is concentric with the second bore, by deflecting the shaft to compensate for eccentricity and misalignment of the second bore relative to the output shaft of the motor.
