The present paper is devoted to the study of the influence of flank wear upon the contact and internal stresses in a single-point tool. A comprehensive model for the distribution of contact stresses along the wear land is proposed and compared with experimental results obtained from photoelastic investigations. For this purpose orthogonal machining of lead was carried out at low speed and constant depth of cut, making use of a transparent epoxy tool provided with a pre-honed wear flat along the flank surface. Wear level and rake angle seem to have influence on both the tool-chip and tool-work contact stresses in differing degrees. The elastic stress field in the tool wedge is evaluated analytically for given mixed boundary loading conditions. These results, on comparison with the experimental data obtained from photoelastic investigation and actual cutting test, indicate noticeable influence of wear level upon contact stress redistribution and stress field reorientation. Based on this, the role of flank wear upon the brittle strength of the tool is clarified.