A method of using a tooling mandrel for assembling a disk drive is described. The method includes providing a head stack assembly including a shaft with an engagement feature, and providing the tooling mandrel including two tooling fingers, one of which is movable. The movable tooling finger is moved between a first configuration in which respective distal tips of the tooling fingers are insertable into and removable from the engagement feature and a second configuration in which the distal tips engage the engagement feature. The tooling mandrel further includes a tooling finger spreader coupled to the movable tooling finger to selectively move the movable tooling finger between the first and second configurations. The method further includes locating the distal tips at least partially within the engagement feature with the tooling fingers in the first configuration, and moving the movable tooling finger to the second configuration to engage the shaft.