The effect of speed on the flank wear of the cutting tool when a nickel alloy is milled is studied. From the analysis of the measured forces, a dynamic semi-experimental model is developed based on the parallelism between the curve of the thrust forces of the unworn tool and the curves when the flank of the tool is worn. Based on the change in the geometry of the contact in the flank worn face, a theory of indentation of the tool on the workpiece is formulated in such a way that upon applying equations of contact mechanics, a good approximation of the experimental results is obtained.