Summary: This paper presents an automatic set-up planning module integrated in a CAPP system for rotational parts to be machined on a lathe. The developed system determines the possible set-up combinations that are necessary for a complete machining of the part as well as the order of each set-up and the surfaces to be used for clamping the part. The applied methodology takes into consideration constraints such as the geometry of both the stock and the final part, the geometry and the capacity of the chuck, and the part tolerances. In general, these constraints allow the system to obtain several valid solutions for clamping the part. Some criteria based on the clamping force and the value of tolerances have been considered in order to establish a preference order among these solutions. Finally, the analysis of linked tolerances and the tool approach direction to each surface determine the sets of surfaces to be machined within each set-up. An example part is used in the course of the paper to illustrate conveniently the methodology, and two additional case studies prove that this methodology is adequate for the solution of real cases.