Abstract
This paper presents formulas for determining the critical depths of cut and asymptotic spindle speed for stable micro milling processes with process damping. The asymptotic spindle speed of a theoretically infinite stable depth of cut is shown to be proportional to the modal natural frequency, radial ploughing constant and radial immersion angle, but inversely proportional to the shearing related cutting constants and tool diameter. These formulas enable identifying the asymptotic speed, absolute stability limit, and in-process radial ploughing constant from experimental stability limits without requiring modal parameters. The presented model is validated by comparison with prior works and verified by experiments.