What Dave says is true...as long as you are referencing from the correct surfaces, variation from centering doesn't matter. As to the metric scale, if you don't work in metric (I recently converted to metric myself and am loving it), it's handy to have a digital caliper in your shop so you can measure thickness in both inches and MM and convert back and forth in a snap. That will make it very easy to use tools that only have metric scales with stock that's already sized to Imperial thickness. They are not expensive, either.