One of the most effective methods for enhancing edge quality is to prevent the tool from exiting the work part in a machining operation. Exit here refers specifically to the tool cutting edges moving out of the part at an edge while removing material. Only entrance burrs are allowed to occur in this condition, resulting in less serious edge defects. This study presents a two-stage geometric algorithm for avoiding tool exits in planar milling of 2D free form contours. The cutter positions causing the tool to exit the part are first detected; then a heuristic scheme is applied to generate new cutter locations with no tool exits. Experimental results show that edge quality is significantly improved. This work provides a feasible method for reducing edge defect in an automatic manner without the need of edge finishing, which is highly advantageous in meso-scale machining.