Patent ID: 7040189

Claim:
A circulation member of a ball screw for circulating a ball rolling on a spiral ball rolling groove formed on a screw shaft comprising: a central portion; and a pair of leg portions disposed at both ends of the central portion so as to extend therefrom, wherein said leg portions have inner peripheries having center lines inclined in directions different from each other with respect to a center line of an inner periphery of the central portion and said circulation member is divided into two parts by first and second division surfaces, said first division surface lying on a plane including a center line of the inner periphery of one of the leg portions and the center line of the inner periphery of the central portion and said second division surface being different from said first division surface and lying on a plane including a center line of the inner periphery of the other one of the leg portions and the center line of the inner periphery of the central portion, wherein the divided two parts have joining surfaces on which a staged portion having difference in level is formed by the first and second division surfaces.