Less mistakes, perhaps but it certainly isn't anymore accurate.
Got to stick my nose in here. I have worked in the "fiber optics" business(splicing), where the "conductors", the fiber strands, were measured in microns. That's metric, the next step below millimeters. There's 1000 microns(micromillimeters) in a millimeter. Most machinists think in thousandths, or possibly tenths. 0.0001 inches. There's 39 thou, and change, to a millimeter. Just that mm isn't the smallest unit of measure there is.
The bottom line, either can be as accurate as the other, it's a matter of what one is most used to. I do both, essentially interchangably. If what I'm working on is metric, I
try to stay metric. Doesn't always work out, but I try. On the other hand, my machines are calibrated in inches. If I was really good, I could work to a tenth of a thousandth. I'm
not that good, but like to try. Further, my model trains are a mixed scale. HO, 3.5mm to the foot. Just how confusing can you get? 3.5mm ~ 0.1385inch. The metric is a little easier to work with here. A similar scale used in Europe is 4mm per foot. It's all a matter of what you're conversant with.
Most of the usage of a dial indicator is to determine out of round, eccentricity, things of that nature. The absolute measure doesn't really matter. As mentioned above, deviation from the "zero" is what matters, get that as small as possible. Whether it's 0.0004 in or 0.1 mm isn't important. Until you're comfortable juggling numbers in your head, a digital caliper does help.
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