This unit introduces the concept of material boundaries in GD&T and explains how they control part fit and assembly. It covers calculation of virtual condition for features of size and explains how boundary modifiers affect tolerance interpretation. Students learn the application and calculation of MMB (Maximum Material Boundary), LMB (Least Material Boundary), and RMB (Regardless of Material Boundary), particularly for datum features.
The unit also compares RMB and MMB applications, explains the simultaneous requirement rule, and teaches how to calculate allowable datum feature shift. Practical applications include performing paper gage calculations to verify functional part acceptance.