Patent ID: 8390953

Claim:
A disk drive device comprising: a hub on which at least one recording disk is to be mounted; the hub having a rotational center; a base rotatably supporting the hub through a bearing unit; and a shaft, which is sleeved inside the bearing unit, placed through an aperture in the hub and fixed to the rotational center of the hub and rotating together with the hub, wherein the shaft has a reduced first outer diameter allowing the shaft to pass into the hub aperture, and a second outer diameter larger than and adjoining the first outer diameter which thereby forms an annular groove around a perimeter of the shaft; the annular groove being formed to have at least one portion composed of a radially extending surface which lies at an acute angle relative to the axis of the shaft and directed in an upward direction toward the hub, wherein when press-assembling the hub to the shaft, a complementary inverse groove that adjoins the annular groove around the perimeter of the shaft in the axial direction and adjoins the shaft along the increased second outer diameter in the radial direction is formed in the hub, and wherein the annular groove of the shaft radially locks into the complementary inverse groove of the hub.