Don't forget, just because you follow the same standard, there still are manufacturer's tolerances. The way a manufacturer manages this tolerance can be very important. one manufacturer may decide that their variance from the mean (i.e. pre tolerance dimension target) is .00X while another manufacturer will use the same standard but decide that their variance shall be .00Z (Z= X/2). The result is that using the same standard the second manufacturer will have a better more reliable, lower variance product than manufacturer 1. Prime example, dodge vs. mitsubishi, engines and chasis built from the same drawings, but one is a piece of junk.