Tolerance Design for Location-Constrained Fits Between Two Parts

This chapter presents the most general type of two-part fits which is the location-constrained fits for single features as well as patterns of features. The concept of fit boundaries is extended to include this type of fit. The fit usually requires multiple datum surfaces named primary, secondary, and tertiary datums. The fit requires the use of position tolerances. The meaning of position tolerances is explained in this chapter. Surface perpendicularity tolerance is necessary to make the datum features define a precision frame of reference. Simultaneous fits require the use of fit datums which are different than contact surface datums.