Abstract Development of methodologies for the geometric characterization of cutting edges is of significant current interest, in light of the profound influence that the edge geometry wields on virtually every machining response, and the evolving capability for generating tailored edges. This paper proposes the parametric modeling of the tool edge geometry through the application of free-knot B-splines that comprise three piecewise segments corresponding to the cutting edge profile and the two tool faces. The transition points that demarcate the cutting edge from the tool faces are objectively and robustly identified by the adaptive placement of the knots that minimizes the residual error from fitting the B-spline to the tool profile data. On identification of the cutting edge, the edge profile is modeled by parametric quadratics to yield four geometrically relevant, contour-based parameters that characterize both symmetric and asymmetric honed edges.