General Carpenters, when I was at school, measured and cut to a tolerance of 1/8th Inch or.125 Inch. . .roughly 3mm. . This appeared to work throughout the house consttruction industry,. . bear in mind that a saw blade was 3mm thick. . window and door frames required some more accuracy of course. . but this was understood.
Then, we Engineers were expected to work to tolerances of a Tenth of a Thou. . .doesn't seem fair does it ? ?