Abstract: A reversing attachment adapted to be applied to a diamond thread screw of the type having intersecting thread grooves, for effecting reversal in the axial direction of travel of a follower associated with the screw, the reversal occurring at any one of a number of predetermined points along the length thereof. The attachment is in the form of an abutment which is positioned at a groove intersection, and which is arranged to engage a driving element of the follower as the latter approaches the abutment so as to prevent passage of the driving element past the intersection. In accomplishing the reversal, the drive element is directly engaged by the abutment, and is caused to shift axially with respect to the follower such that the element transfer from one groove of the diamond thread screw to the oppositely-directed groove.