a coupling assembly includes a first portion and a second portion which are configured to couple to one another such that the second portion is capable of rotationally driving the first portion about an axis of rotation. The first portion is provided with a first magnet and the second portion is provided with a second magnet. The first and second magnets are arranged to repel each other such that the first and second portions are biased away from each other in an axial direction that is parallel to the axis of rotation.