A method is proposed for predicting the internal thread height as a function of tapping process faults and relating it to the standardized thread quality tolerances. Based on the mechanistic tapping model [6], a method of estimating the magnitudes of the faults has been proposed. The effects of tap-hole axes misalignment and tap runout on thread height have been revealed by the mechanistic tapping process model. Based on this model and data obtained from the process estimated process fault values have been used to predict thread height and then predict thread pitch diameter. Using standard tolerances for pitch diameter, an assessment of thread quality can then be made. Validation experiments have been run on several materials for different combinations of process faults. Results of thread measurements showed excellent correspondence with the model predictions.

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