Abstract: A ball screw device includes: a threaded shaft; a nut; multiple first balls rollably arranged on a helical raceway composed of a helical groove of the threaded shaft and a helical groove of the nut; an inner ring raceway groove formed on an outer circumferential surface of one axial end of the threaded shaft; an outer ring having an outer ring raceway groove that faces the inner ring raceway groove; and multiple second balls rollably arranged between the inner ring raceway groove and the outer ring raceway groove. The ball screw device converts rotation of the threaded shaft into linear motion of the nut through the first balls rolling on the helical raceway while being subjected to a load. The outer ring has a rolling element insertion hole penetrating from its outer circumferential surface to the outer ring raceway groove and a lid configured to cover the rolling element insertion hole. An inner surface of the lid is formed into a concave shape to serve as part of the outer ring raceway groove.

Abstract: There is provided a ball screw, a machine tool, and a conveying device that achieve the suppression of the vibration even when the nut rotates at high speed and the reduction of the manufacturing cost. The ball screw includes a screw shaft, a nut body, rolling bodies, a synthetic-resin covering member, and a circulation member. The covering member has a tube shape arranged coaxially with the nut body to cover the outer peripheral surface of the nut body. A groove part formed on the inner peripheral surface of the covering member and the outer peripheral surface of the nut body form a rolling-body return path. The covering member is provided with an engagement part engaged with a cutout part formed on the outer peripheral surface of the circulation member.