This; also, the more interesting tidbit is that the US at that point hadnt really developed anything with titanium (for the same reason; most of it was in the U

This; also, the more interesting tidbit is that the US at that point hadnt really developed anything with titanium (for the same reason; most of it was in the USSR) so Lockheed had to develop all the tooling for the SR-71 internally as well, just to be able to work with it --regular steel tools simply couldn't handle titanium. +1 on the "Skunk Works" book just for the stories...