Your way, TP, is for sure the better way of doing it but if you lack a dial indicator the next best thing is to use a digital caliper and measure it the way I described it. Theoretically they both should show the same results all be it the caliper way will, most likely, not be as precise since there is the human factor involved but that should be only a thou or two and I'm not worried about that right now. First I'd like to solve the general problem and then I'll teak it.