working regardless of the size of the lead angle of the external thread 22 b on the adjustment nut 22 in addition by making an appropriate setting of the gap u03b4 the backlash can easily be changed in one example of a manufacturing method for the clutch ring 240 a two step forming is conducted by blanking to snap a ring form to be the clutch ring 240 out from a coil material with a predetermined width and by drawing the clutching section 242 and bending all plate teeth 243 a simultaneously however the manufacturing method and the number of process for the clutch ring 240 are not limited to what is described herein another embodiment of this invention is explained next for the explanation of this embodiment identical members from the first embodiment have the same reference numbers except for the clutch ring 340 and the explanation of identical members will be omitted here fig6 8 show the clutch ring 340 with different shapes of plate teeth the clutch ring 340 comprises a ring shape clutch section 342 integrally formed from a thin metal plate material by press and toothed portion 343 having plate teeth 343 a projecting toward an axial center at predetermined intervals formed in a center opening of the clutch section 342 side surfaces 343 c are located on both sides of the plate tooth 343 a and are formed in a direction to cross the thread groove.