Abstract: A spindle motor comprises a fixed shaft member, a sleeve, and an annular chucking portion. The fixed shaft member has an annular collar protruding outward from and substantially perpendicular to the outer peripheral surface of said fixed shaft member, and also has a thrust flange provided a specific distance away from said annular collar. The sleeve component is monolithic with a hub component The annular chucking portion is formed to include a surface along an axial direction outside said thrust flange in a diameter direction of said thrust flange. The annular chucking portion is disposed at a position in an axial direction that includes a vertical position of a surface to which said disk is attached.

Abstract: Object: A spindle motor of the type in which both ends of a shaft are fixed has a structure in which both ends of a hydrodynamic bearing are open to the atmosphere, and when the rotational precision of rotating bodies is poor, the bearing is subjected to a great deal of fluctuating stress, and leakage of the lubricant occurs. Means for Solution: In a spindle motor having a fluid bearing in which a narrow gap is formed between the surface of a fixed shaft member and a sleeve component (rotating member), and this gap is filled with a lubricating fluid, the shaft member has an annular collar formed so as to protrude substantially perpendicularly to the cylindrical surface of the shaft member. The rotating member is such that the sleeve component fitted over the shaft member is constituted integrally with a hub component that fixes a magnetic disk, and an annular seal member is fixed to the upper end side of the shaft member.