For tool machinery design, the type of machine structure plays an important role in its final machining precision. In the marketplace, structure types change very quickly because of different application purposes and customers’ requirements. Moreover, to develop new and good machine structures, designers usually pay too much time and money in the work of trial and error. For a quick response to market needs, machine makers should find time-saving and money-saving ways to optimally design and verify their products, and accordingly build a reliable database for further modifying and developing new models. In this study, we propose a hybrid design procedure that uses experience and know-how as initial design bases and, together with an optimal Taguchi-based finite element method (FEM), rapidly and efficiently obtains a highly rigid structure. To verify the simulation results, experiments using displacement sensors are also performed. Specifically, in this study, we chose a long-based computer numerical control (CNC) grinding machine as the target because it is a challenge to attain machining precision owing to its weakness feature of a long and narrow structure. With this proposed methodology, machine designers may efficiently and quickly determine the optimal structure of similar types of CNC machine tools.