<p>Ultrasonic cutting is an advanced machining technology applied to Nomex honeycomb cores. However, during the finishing process, machining errors exceeding the allowable tolerances occur owing to the lack of an effective path planning method. This study addresses this issue by examining tool path planning for finishing off various typical honeycomb core features. Initially, a theoretical and experimental comparison of the residual heights of the honeycomb core plane features revealed that machining accuracy was superior along the double-wall direction to that along the perpendicular double-wall direction. Thereafter, the theoretical model of the plane features was used to predict the residual heights of the lead angle in the range of 0°–0.5° along the double-wall direction. In addition, theoretical models for residual height were derived for convex and concave surface features using transverse and longitudinal cutting methods, respectively. This study introduces algorithms for tool interference checking and tool posture adjustment to determine the critical lead angle preventing interference. By integrating these algorithms, a honeycomb core finishing path planning processor was developed on the MATLAB platform. Finally, simulations of the solid model were performed using VERICUT software to verify the feasibility of the proposed algorithms. Actual machining of honeycomb core feature parts demonstrated that the developed finishing processor had the ability to achieve high-precision results.</p>