I found some great quotes about the importance of tolerances. They exemplify the importance and impact of GD&T.

tol_design.jpgTolerances have far more impact on cost, quality, and customer satisfaction than they have traditionally been accorded. Often during product design, the focus is on the nominal specification and its effect on functional quality.

The discipline and clarity that GD&T brings to the tolerancing task in undisputable. The methods of GD&T are profoundly useful in communicating tolerances, and play a critical role in how tolerances are ultimately relayed to the manufacturing community.

– C.M. Creveling

Tolerance Design – A Handbook for Developing Optimal Specifications