Patent ID: 7721445

Claim:
A method of manufacturing a thrust plate having an annular shape and fixed to a shaft of a fluid dynamic bearing mechanism, the method comprising steps of: a) preparing a work piece having a plate-like shape with one axial surface and other axial surface substantially parallel to each other; b) forming a middle concave portion having a circular outer rim centered on a center axis substantially perpendicular to the one and the other axial surfaces of the work piece; c) forming an annular concave portion having an annular shape with a radially outer rim and a radially inner rim centered on the center axis in the other axial surface of the work piece and arranged radially outside of the middle concave portion; d) cutting a portion radially inside of the circular outer rim of the middle concave portion away from the work piece along the circular outer rim by press working, in which force directed from the one axial surface to the other axial surface is applied to the portion radially inside of the circular outer rim, to form an inner circumferential surface of the thrust plate; and e) cutting the work piece at a portion radially between the radially outer rim and the radially inner rim of the annular concave portion by press working, in which force directed in the axial direction from the one axial surface to the other axial surface is applied to radially inside from the portion between the radially outer rim of and the radially inner rim of the annular concave portion, to form an outer circumferential surface of the thrust plate.