A pivot bearing structure formed of a leaf spring is incorporated into a rocker or force transmission member which whenever mounted to a carriage of a high density data tape drive system precisely defines the pivot axis of the rocker and provides a very high degree of stiffness in a vertical plane, that plane being parallel to the recording surface of the magnetic tape. The rocker derives motion from a voice coil motor (VCM) and transmits that controlled motion to a magnetic head which is suspended for movement in a vertical plane while in contact with a length of magnetic tape upon which data is recorded or from which data is read. The movement of the magnetic head may be very precisely controlled by energizing the VCM, because the pivot axis is extremely well defined due to the stiffness in the vertical plane of the pivot bearing. Movement of the VCM coil directly translates into movement of the magnetic head. The rocker is fabricated to form a cavity or pocket exposing a portion of the leaf spring to permit the bonding of another part to the leaf spring.