Abstract: A nut on a helically threaded steering shaft, held against rotation, carries a first set of involute teeth meshing with a second set of involute teeth on an adjoining gear sector which pivots on an axis skew to that of the shaft. The two sets of teeth have centers of curvature offset from the sector axis but aligned with that axis in a midposition in which they engage each other without play; upon a shift of the nut to either side, the tooth clearance or backlash increases progressively while the transmission ratio either increases or decreases, depending upon the relative positions of the two centers of curvature and the sector axis. In a limiting case, the radius of curvature of one set of teeth is infinite.