Towards Right-Sized Limits: A Beginner’s Primer for Rationalizing Build Tolerances

Abstract

In activities such as aerospace tool building the tracker operator is often faced with a demand to build to extremely tight, perhaps even impossible, tolerances. Although there are many unknowns it is possible to estimate the uncertainties associated with any measure and build activity. Taking the time to analyze these factors prepares the engineer for a discussion with the customer about appropriate tolerances and can help avoid making accuracy promises which cannot be kept. It is also a good opening for discussions on the high cost of tight tolerances and the use of local coordinate frames, relationship fitting and other metrology tools to create a more sustainable fixture—in a word, to rationalize the build tolerances.