I remember reading a story a few years ago that during the latter part of WW2 when Rolls- Royce and Packard were both building the Merlin engine Packard sent over to Derby a drill so many microns thick with a look how clever we are, Rolls Royce sent it back with 3 holes drilled in the shank.
I bet they could have put a blob of weld on a 1.4 mm screw!!
H