Patent ID: 8087974

Claim:
A manufacturing method for a worm gear reducer including a worm wheel ( 5 a ) and an operational worm ( 3 ), wherein the worm wheel ( 5 a ) is meshed with said operational worm ( 3 ) at usage, comprising the steps of: preparing an operational worm ( 3 ) comprising teeth; preparing a worm wheel ( 5 a ), in which at least a surface layer of a tooth portion ( 8 a ) is made of synthetic resin; preparing a machining worm ( 13 ), in which pitch of teeth of the machining worm ( 13 ) in an axial direction thereof is the same as that of said operational worm ( 3 ), and providing abrasive grains ( 14 ) on a surface of the machining worm ( 13 ) by means of electro-deposition; disposing the machining worm ( 13 ) in a twisting position relative to the worm wheel ( 5 a ); and rotating the machining worm ( 13 ) and the worm wheel ( 5 a ) with meshing each other so as to machining the tooth portion of the worm wheel ( 5 a ), wherein said operational worm ( 3 ) and machining worm ( 13 ) are prepared such that the diameter of the tip and root portions of the machining worm (D 13a , d 13a ) are larger than the diameters of the tip and root portions of the operational worm (D 3 , d 3 ) by 1 to 10%.