A tire sidewall is that section of the tire that bridges the tread and the bead. It is difficult to manufacture tire sidewall molds with a three-axis CNC machine, because the letters on the sidewall should be engraved perpendicularly to the sidewall surface. In this paper, a four-axis lettering machine that efficiently engraves letters and patterns on the sidewall mold is proposed. A bending projection algorithm is introduced to project letters on the sidewall surface without distortion. The procedures to cut letters and patterns using the four-axis lettering machine is proposed: (1) measuring the profile curve using a mechanical probe, (2) using a bending projection algorithm to project letters onto the sidewall surface without distortion, (3) generating the four-axis CL data, and (4) calculating the inverse kinematics to generate NC codes. The procedure is implemented using a PC-NC (Personal Computer Numerical Control) system, which has an open architecture based on the personal computer. The results demonstrate that the method is useful for manufacturing tire sidewall molds.