When I started my apprenticeship at BSA Birmingham UK 1965 almost the first thing we had to do was take a block of steel 3x3x3 inches and had to file only make it square and true in all directions. This is very difficult to do and you scrap a few till it comes off. But afterwards you always remember how to file (holding it and body position is important). Spoke to some German engineers and they had to do the same thing. Just shows the difference between the two continents cultures US wants to machine everything.