Abstract
A method is developed for selecting the dimensions and tolerances of mating parts and the precision of the process equipment with regard to the performance of the alignment phase of many processes, for example assembly. A formula is presented which expresses the performance as a function of the size ratio and tolerances of the objects being mated and the precision of the equipment. Non-dimensional tolerances and precisions provide a means to present graphically the underlying relationships in a useful yet general form. In situations where the equipment precision is given a priori, maximum allowable size ratio tables provide a method for determining the part dimensions and tolerances that will enable the equipment to mate the parts successfully. Assembly process application examples are given.