Mechanical actuator latch subassembly with overcentering spring for a disk drive

A head disk assembly for a hard disk drive having a mechanical actuator latch subassembly. The head disk assembly includes an enclosure, a disk, a pivot bearing cartridge, and a head stack assembly. The enclosure includes a base that preferably includes integral side walls. The disk has a recording surface that has an annular landing zone. The head stack assembly includes a head supported to be moved radially relative to the recording surface and to be brought to rest at a position in the landing zone. Significantly, the head disk assembly also includes a unitary latch base member and a unitary pivot latch member. The unitary latch base member has a mounting portion for mounting the latch base member to the base, an arm extending parallel to the major interior-facing surface, an inner crash stop post including an engaging end, and a pivot post. The arm also includes a spring holding post. The unitary pivot latch member has a bore surrounding the pivot post to allow pivot motion of the pivot latch member. The unitary pivot latch member also includes a receiving surface, a latch surface and a spring holding mount. In one embodiment, the head disk assembly also includes a spring for biasing the unitary pivot latch member in a latched or an unlatched position. The head stack assembly also includes a tang which engages the engaging end and the latch surface to define an inner crash stop and latch.