ABSSAC's self-reversing screw product does not require the driven screw to change its direction of rotation to enable the nut to return to its original start position. The reciprocated bi-directional movement is achieved by using a follower blade in the nut, that is matched to the particular groove width and screw turn round on the screw. (Our self reversing screws, do not utilise ball bearings in their linear travel). The video shows the basic mechanics of the design we utilise. www.abssac.co.uk