I have a conversion chart that helps immensely. Metric is fine, I have worked in it several times, but the majority of my work was in tenths. CNC, manual mill, Lathe, but mostly Solidworks.
Fractions are great for houses, but not so great for fine work. All my scales are in tenths, as are all my calipers...which I use almost exclusively out to 12".
For the most part, I can convert in my head, but occasionally I see the odd fraction that hits me sideways...
Just used to years of decimal prints. I am muddling along and will continue.