In pocketing with contour parallel (CP) paths, the cutter encounters a varying engagement with the workpiece, which causes variation in chip load and cutting forces. This varying cutting force naturally leads to the variation of tool deflection, hence impairing machined surface accuracy. This paper presents a new tool path modification scheme, which regulates a constant cutting engagement with workpiece in 2.5D end milling. The semi-finishing path, the path prior to the finishing path, is modified by the proposed scheme such that the engagement angle along the finishing path is regulated at a desired level. By maintaining cutting engagement constant, the cutting force can be regulated approximately constant, thus minimizing the variation of tool deflection, and improving machining accuracy. The improvement of machining accuracy by applying the new tool path modification scheme is experimentally validated for the case where the proposed scheme is applied to pocketing. The machining results are analyzed and compared with the cases with conventional contour parallel path and the feed rate control scheme applied in pocketing.