An assembly for breaking up vascular thrombus or other obstructive material including a motor housing having a motor, a motor shaft extending from the motor, a first housing positioned at a distal end of the motor shaft, a rotational thrombectomy wire and a second housing positioned at a proximal end of the wire. The first housing has a first magnet positioned therein and recessed from the distal edge of the first housing which has a first plurality of teeth. The second housing has a second magnet positioned therein and recessed from a proximal edge of the second housing which has a second plurality of teeth intermeshing with the first plurality of teeth when the wire is coupled to the motor shaft. The first and second plurality of teeth slip when a torque of the motor shaft exceeds a predetermined value.