<p>The distribution of residual stress directly affects machining deformation, influencing the precision and integrity of the finished product. During the ball-end milling process, the relations between the residual stress distribution and cutting parameters are quite complex, which limits the potential for further controlling the deformation of machined parts. In this paper, a series of milling experiments were conducted with different tool orientations to further investigate the influence of cutting speed direction on the circumferential distribution of residual stress. The tool orientation related to cutting speed resulting in residual stress is analyzed to guide milling experiments, and the experiment results have shown that the direction of the maximum residual stress is located within 30° counterclockwise in the reverse of the cutting speed. The milling surface shows an anisotropic characteristic with a range of surface residual stresses from 41 to 164&#xa0;MPa. The stress distribution presents an asymmetrical elliptical shape, where the long axis is near the cutting speed direction. To verify the findings, the mechanism of the residual stress variation is discussed by comparing the cutting forces. With the help of the experimental results, the distribution and the maximum direction of the residual stress can be optimized by adjusting the tool orientation.</p>