For those that only dabble in math then sure the Metric system works but for those who have to apply said math then it sucks. If you ever had to work off a print that was converted to inches from metric or inches to metric you would see the light. That and still today most measuring devices are still inch. Add to this that often the smallest dimension on metric measuring devices is .5 MM which is 0.019685, kind of coarse actually when your tolerances are inside .001. .1mm is still more than .003 inch at 0.003937. Face it for making tight tolerance parts metric is not as easy to use. This all said when the inch is divided into thousandths all the way out the math is just as simple as the math for metric.
Therein lies the rub. It is not the working in metric which is difficult. It is the jumping back and forth, and remembering all the conversion factors.
If the US had adopted metric 100 years ago, there would be no need for making conversions. The only time you would need to even think about an SAE measurement might be if restoring some machine 100 yrs old, made before the conversion.
