Digital Dan: I got to inspect (up close!) an SR-71 at an air show long ago north of Seattle (supposedly this was the first airshow the SR-71 attended and it was "standing room only" because of that!).
Anyway I used to be a mechanic on the wonderful Boeing 727 airplane and installed MANY a countersunk rivet.
I am taller than the average Joe and I went to the nearest point to the roped off plane that was allowed - I inspected the wing leading edge and nearly fainted - the countersinks were uneven, sloppy, chattered and many were way to deep - only a few were NOT deep enough.
My curiosity was so piqued that after a while I stretched out and reached up with my index finger and felt the overly deep and chattered countersinks to verify what my eyes were seeing.
I did so and immediately the armed military guards confronted me and ran me off. Apparently it was "verbotten" to touch said secret airplane at the time.
It took me hours to figger out why and how the production crews/inspectors would allow such un-aerodynamic work to exist on a plane that flew so fast - it came to me that I had installed parts on the 727 that were made of Titanium and indeed the countersinks ALL chattered (due to the extreme hardness of that metal) and it was VERY difficult to get a good countersink - whereas on aluminum my countersinks were of perfect depth and smoothness.
The bottom line was that Titanium is so strong and heat resistant that the imperfect countersinks were of a no-nevermind.
I even went back and paid to get back in the day after the air show to watch the SR-71 "take-off"! It was a sight and sound to behold - well worth the money and effort to see.
Hold into the wind
VarmintGuy
