Stability and surface location error are investigated numerically for milling operations with a helical tool. A detailed mechanical model is derived that includes both surface regeneration and the helical teeth of the tool. The governing delay-differential equation is analyzed by a modified version of the semi-discretization method. The surface location error is predicted based on the (stable) forced motion of the tool for different axial depths of cut. It is shown that the surface location error varies periodically along the axial direction due to the helical teeth. The relation of the maximum surface location error, the surface waviness and the surface roughness is explored