Rout stopped cuts with stopblocks
Edge cuts, such as chamfers, and surface profiles, such as flutes, sometimes need to start and stop precisely and uniformly. That's the time to use simple, customized stopblocks to control where the profile starts and stops on each workpiece. Measure from the point where the cut will stop to the end of the workpiece, subtract the bearing radius, and cut the stopblock to that length from scrap at least 3/4" thick. Clamp the stopblock to the edge of the workpiece as shown.