Process Tolerance Analysis is used to compute the accumulation of operation variations and to predict if manufactured components will meet required tolerances. The analysis can also be used for process design. A GM Powertrain software tool, Process Planning System-I (PPS1), has been developed for tolerance analysis of turned parts. PPS1 uses ICAD® software to read Unigraphics (CAD) and manufacturing data, and generates a minimum stock size needed to support machining, in-process dimensions, and stock-removal tolerances. PPS1 has reduced analysis time, eliminated calculation errors, and improved manufacturing plans. The analysis procedure and PPS1 are described.