Magnetic head positioner for a magnetic disk apparatus minimizing thermal offtrack

A magnetic head positioner for a magnetic disk apparatus, comprising:

• an arm holder rotatably supported on a shaft by a plurality of bearings and providing a plurality of arms carrying magnetic heads for writing and reading data at tip ends thereof;
• a first cylindrical sleeve interposed between said bearings and said arm holder and fixed to the outer peripheral surface of said bearings, and being made of a material having substantially the same linear expansion coefficient as that of said shaft;
• and
• a pair of second cylindrical sleeves interposed between said bearings and said arm holder, each fixed to said first cylindrical sleeve at one end portion thereof and to an inner peripheral surface of said arm holder at the other end portion thereof, and being made of a material having substantially the same linear expansion coefficient as that of said arm holder;
• wherein said first cylindrical sleeve has first grooves for engaging with said second cylindrical sleeves at both ends, each of said pair of second cylindrical sleeves having a second groove for engaging with said first cylindrical sleeve at one end, said first sleeve and said pair of second sleeves being fixed to each other by press fitting with engagement of said first and second grooves.