Tolerance Design for Unconstrained Fits Between Two Parts Part I: Fit Formulas

This chapter presents the simplest type of fit, known as unconstrained fit, and develops the simple equations that assure such fits. The geometric meaning of the size limits applied to features of size for cylindrical and parallel-plane fit features is presented. The concept of fit boundary which is critical to understanding of two-part fit problems is discussed in this chapter. The general format of specifying geometric tolerances and various types of geometry control statements is discussed. The gage-based method of interpreting geometric tolerances is used to demonstrate the meaning of straightness and flatness tolerances. The use of and advantages of using zero geometric tolerance in fit problems is also presented.