An analytical force model is presented to simulate the cutting force and the chip flow direction in the drilling process. Three dimensional chip flow is interpreted as a piling up of the orthogonal cuttings in the planes containing the cutting velocities and the chip flow velocities. The chip flow direction is determined to minimize the cutting energy. The simulation is performed to discuss the effect of the lip geometry on burr formation at the backside of the plate. Burr formation is associated with the thrust and the chip flow direction. The curved lips drill is examined to reduce the thrust and control the chip flow with the orientation and the curvature of the lips. The counterclockwise orientation with the small curvature is effective in reducing burr formation in the simulation. A drill is designed to have the counterclockwise curved shapes on the straight lips. The designed lips flow the chip upward to avoid the chip clogging in the steady process. Then, the curved shape at the end of the lips control the chip flow toward the radial direction of the tool to reduce burr formation with the thrust around the end of cut.