Precision should always be considered as how much is necessary, and why. Functionality is the ultimate judge! I have watched mold making in this country migrate offshore since the 80's due to cost benefit. Medical mold making remains relatively strong due to liability issues. As one becomes familiar with the significance of the effects of geometrical precision ... squareness, concentricity, parallelism, perpendicularity, etc., combined with good tolerance application based on loads, forces, deflection, thermal, etc. we become more successful in our machining outcome. We don't need a degree in some type of engineering, but a well-rounded understanding of how the device behaves and reacts in its working environment. That's part of the fun of model engineering, isn't it? Sorting out what works sometimes comes from empirical testing, which is fun too! As we learn, we become more proficient in what's going on, firsthand, on a focused area, model engineering. We become the engineer. That's why many of us likely enjoy our hobby.