Abstract: Ball swaging is a material process used to assemble a boss tower and an arm aperture. A swage ball is inserted into the boss tower to swage and couple two components. The swage ball has a larger diameter than an inner diameter of the boss tower, applies a compression force to the inner surface of the boss tower to hold both components together with adequate holding force and without damaging the boss tower. This study proposes a new design of the boss tower by relief ring width optimization. It reduces the arm tip deformation while avoiding HSA resonance and allows similar swaging quality by using single ball. The 3-D FE method was used for analysis. The result analysis and experiment show boss tower deformation very similar. Although the variation of CTQ has been decreased, cleanliness has been improved. Moreover, non-circular arm aperture is able to reduce swage effect.