A head stack assembly (HSA) having an actuator comb with a stepped inner bore may have an upper portion of the inner bore with a first diameter that is greater than the diameter of a lower portion of the inner bore. Therefore, little friction and resistance is encountered when force fitting a pivot-bearing assembly into the upper portion of the stepped inner bore, thereby avoiding surface damage and the generation of unwanted debris particles. The HSA may further comprise a plurality of tolerance rings to couple the actuator comb with the pivot-bearing assembly, such as one tolerance ring positioned below the step feature and one tolerance ring positioned above and seated on the step feature of the comb inner bore.