High-efficiency machining and high-quality cutting are required in mold and die machining. To produce high-quality molds and dies, we require high rigidity for cutting tools and machining with effective cutting edges. We propose tilted tool axis machining, which involves indexing using 2-axis rotary motion and machining using 3-axis feed motion on a 5-axis machining center. To conduct tilted tool axis machining by ball end mill, we must know the tool attitude to ensure stable cutting and how to control the tool attitude to stable cutting conditions. Our main objective was to clarify the tool attitude ensuring stable cutting conditions and to develop automatic determination of the indexing angle for mold and die machining. We start by discussing machining experiments using a dynamic force dynamometer on a 5-axis machining center to analyze machining features using a tilted tool axis ball end cutting tool. We then determine machining evaluation from which the results of machining experiments are determine using a tilted tool axis ball end cutting tool. We propose calculation of optimum indexing angle candidates for machining surfaces using normal vectors of surfaces and cutting edges. We then show machinable area evaluation for the calculated indexing angle based on inverse offset method with a state flag. We then give examples demonstrating the effectiveness of our proposal.