A hard disk drive utilizes a spacer ring at its inner diameter to load and unload
the read/write heads. During relatively small shock events, the actuator is retained
relative to the disk through a circumferential groove in the spacer ring. A complementary
protrusion on the load/unload tab extends from the actuator into the groove to
complete the retention. A tribological coating on the spacer ring and/or protrusion
significantly reduces wear therebetween. However, during large shock events an
inertial latch is used by the system to hold the actuator in place.
