Tolerance Design and Analysis of Multipart Fits

This chapter presents the design and analysis of fits involving more than two parts or the special case of two parts clamped together by fasteners. The design of tolerances for multipart fits is more time-consuming as they simply involve more parts and more features. The analysis of multipart fits is also more time-consuming and more difficult than two-part fits as the simple technique of using fit boundaries no longer works. The more general analysis applicable to multipart fits requires developing one or more tolerance loop equations for each fit requirement. These equations are made up of vectors that can be multidimensional, but one-dimensional tolerance loops cover most applications. The solution of these vector equations leads to the selection of basic sizes and tolerances that guarantee fit. Graphical solution method is an alternative to forming loop vector equations and despite being more time-consuming is often preferred by practitioners.