A side note re composites - cutting repair
Cured composites as in the 787 can be lightly sanded- BUT for any serious work as in drilling or cutting, either carbide and or diamond abrasive tools are needed.
For example regular HSS drills wear very rapidly in just a few holes- although some specialized surface treatments reduce the wear factor.
One of the problems in the normal cutting and trimming of composites was the abrasive dust involved in trimming large panels at a reasonable rate wtih high speed cutters.
In the 1980's- I designed a brazed diamond cutter " grinder " which was used to cut major composite sections of the B2
Several years earlier- another BA employee designed a carbide drill for similar material looking like a sharp pointed fluted reamer.
I mention this cuz most seem to think that carbon composite is easily cut. yes pure carbon threads can be cut- But when combined with epoxy like material and cured, its a whole different story.
Yes one can take a normal HSS drill used on aluminum and steel and drill a hole or two or three - but then the diameter of the drill will be somewhat less than when started. In a production environment - this is unacceptable.
And yes - industrial diamonds can be brazed on steel tools ..