Countersinking the fuel tank skin (top and bottom) where it rivets to the rear baffle. Mary was helping by lending moral support! I used a cordless drill as it as more torque than the airdrill and therefore doesn't "chatter". Makes a nice countersink. I countersink where I just had a tiny silver ring around the rivet when I dropped on into the rivet hole. Perfectly flush.
Machine countersinking the skin to baffle rivet line.
