Abstract: In a ball screw, a nut is fitted with the outer periphery of a screw shaft, ball rolling grooves opposed to each other are formed in the screw shaft and the nut The ball rolling grooves cooperate in forming a ball rolling path therebetween. A tube as a return path disposed on the nut for connecting one end portion of the ball rolling path to the other end portion thereof, the ball rolling path and tube cooperate in forming an endless circulation path. A plurality of load balls are disposed within the endless circulation path. The position of the tube cannot be limited to a single specific position. In the ball screw, retaining pieces are respectively inserted between the mutually adjacent ones of the load balls disposed within the endless circulation path.

Abstract: In a ball screw, a nut is fitted with the outer periphery of a screw shaft, ball rolling grooves opposed to each other are formed in the screw shaft and the nut The ball rolling grooves cooperate in forming a ball rolling path therebetween. A tube as a return path disposed on the nut for connecting one end portion of the ball rolling path to the other end portion thereof, the ball rolling path and tube cooperate in forming an endless circulation path. A plurality of load balls are disposed within the endless circulation path. The position of the tube cannot be limited to a single specific position. In the ball screw, retaining pieces are respectively inserted between the mutually adjacent ones of the load balls disposed within the endless circulation path.