Patent ID: 8537498

Claim:
A baseplate of a suspension fixed to an actuator arm of a disk drive, the baseplate being formed from heat-treated austenite stainless steel and comprising a cylindrical boss portion configured to be inserted into a mounting hole formed in the actuator arm, wherein: the boss portion comprises a ball insertion hole, which penetrates the boss portion along an axis thereof, and a chemically-polished surface formed on an inner circumferential wall of the ball insertion hole, the chemically-polished surface has an oxygen-rich layer of which an oxygen concentration is higher than a chromium concentration near a surface, a thickness of the oxygen-rich layer is thinner than a thickness of an oxygen-rich layer of a non-chemically polished surface, and a frictional resistance when a ball is inserted in a direction in which the boss portion is pulled is smaller than a frictional resistance when the ball is inserted in a direction in which the boss portion is compressed.