A spindle motor configured to be used for a hard disk drive device with a gas having a density lower than a density of air sealed in an internal space includes a rotor magnet. The rotor magnet has a radial thickness of 1.0 to 1.4 mm and a density of 5.6 to 6.0 g/cm.sup.3.

A hub of this motor includes a hub annular portion being annular and arranged above a stator, and a flange portion arranged to extend radially outward from the hub annular portion, and including an upper surface on which an annular member is arranged. A yoke includes a first yoke cylindrical portion to which a magnet is fixed; a yoke annular portion arranged to extend radially inward from an upper end of the first yoke cylindrical portion, and including an upper surface arranged opposite to a lower surface of the hub; and a second yoke cylindrical portion arranged to extend axially upward from a radially inner end portion of the yoke annular portion. An inner circumferential surface of the hub annular portion and an outer circumferential surface of the second yoke cylindrical portion are fixed to each other at an engagement portion arranged radially inward of a radially inner end portion of each of coils.

A sintered metal bearing is formed through sintering of a compact obtained through compression molding of raw-material powder. The sintered metal bearing includes chamfered portions that are respectively formed at least along outer rims of both end surfaces of the sintered metal bearing, and a dynamic pressure generating portion formed on an inner peripheral surface of the sintered metal bearing by sizing. An axial dimension of each of the chamfered portions is set larger than a radial dimension of the each of the chamfered portions, and a difference in axial dimension between the chamfered portions on one end side and another end side in an axial direction of the sintered metal bearing is set larger than a difference in radial dimension between the chamfered portions on the one end side and the another end side in the axial direction.

Aspects of the disclosure provide for mitigating a coefficient of thermal expansion (CTE) mismatch between glass components and adjacent metal components in a disk storage device to improve thermal and shock performance. The methods and apparatus provide a hub, provide a first recording disk comprising a glass material and a center hole on the hub such that the hub extends through the center hole of the first recording disk, provide a first spacer on the first recording disk, the first spacer comprising a nickel-iron alloy, and provide a second recording disk comprising a glass material and a center hole on the first spacer such that the hub extends through the center hole of the second recording disk, wherein the first recording disk and the second recording disk each comprise a magnetic recording layer configured to store information.

Aspects of the disclosure provide for mitigating a coefficient of thermal expansion (CTE) mismatch between glass components and adjacent metal components in a disk storage device to improve thermal and shock performance. The methods and apparatus provide a hub, provide a first recording disk comprising a glass material and a center hole on the hub such that the hub extends through the center hole of the first recording disk, provide a first spacer on the first recording disk, the first spacer comprising a nickel-iron alloy, and provide a second recording disk comprising a glass material and a center hole on the first spacer such that the hub extends through the center hole of the second recording disk, wherein the first recording disk and the second recording disk each comprise a magnetic recording layer configured to store information.

A disk hub is configured to retain a magnetic recording medium including an annulus shape and a layer configured for magnetic recording. The disk hub includes a base plate portion for supporting an inner diameter area of the magnetic recording medium and a stem portion on the base plate portion. The stem portion includes a frustoconical portion on the base plate portion and a top portion on the frustoconical portion. At least the top portion of the stem portion includes a material with a hardness less than that of stainless steel. The disk hub can reduce surface damages (e.g., scratches) on the media surface during media testing.

To provide an outer rotor type motor capable of suppressing the runout of a top surface by improving the strength in a fitted part between a rotor yoke and a rotor shaft and suppressing resonance between vibration generated by rotation of a rotated body to be a load and motor vibration to thereby realize noise reduction. A rotor yoke is configured so that a rotor hub is fitted to a top surface portion formed in a cup shape integrally with a rotor shaft, and a reinforcing hub concentrically fixed to the rotor shaft with the rotor yoke is arranged so as to overlap the rotor hub.

A protrusion includes a leading end to which a yoke is fixed and a connector that connects an axially lower end of a flange and the leading end. A minimum width of the connector in a direction intersecting a direction in which the protrusion protrudes is smaller than a maximum width of the leading end in a radial direction. A radial position at a radially inner end of the leading end is located radially outward with respect to a side surface in a radially inward direction of a magnet.

A magnetic disk device includes a plurality of disk-shaped magnetic disks 30, spacers 80, a hub 90, a clamp 70, and a fastening member 72. Each of the magnetic disks 30 includes a through-hole in a center section thereof. Each of the spacers 80 includes a through-hole in a center section thereof, and is disposed among the magnetic disks 30. The hub 90 is inserted into the through-holes of the magnetic disks 30 and the spacers 80. The clamp 70 presses and holds the magnetic disks 30 and the spacers 80. The fastening member 72 fastens the clamp 70 to the hub 90. The clamp 70 is fastened to the hub by the fastening member 72 with a torque of from 5 cN.Math.m to 45 cN.Math.m.

A yoke includes a first cylindrical unit held by a radially outside surface of a rotor base, a yoke annular unit extending radially outwardly from an axially lower end of the first cylindrical unit, and a second cylindrical unit extending axially downward from a radially outer end of the yoke annular unit, and a magnet fixed to a radially inside surface of the second cylindrical unit.