Well next on my list was inspection covers. I spent a good part of the day trying to figure out the best way to mount the nut plates on the inspection cover backing flange. I couldn't find any definitive guidance so I experimented a little. I wasn't sure if it is preferred to machine a countersink for the nut plate rivets and center screw on the flange rather than dimple?
If you dimple the flange the nut plate sits on top of three mounds. It's actually easier to dimple but I'm not sure I like the nut plate sitting on the mounds. To make it work you actually have to bend the legs a little since the rivet dimple doesn't crown as much as the screw dimple. Machining a counter sink would be more work but the nut plate would sit flat on the backing. The countersink for the screw actually cuts into the nutplate a little to account for the dimple to fit into it.
I decided to ask the group. I got mixed answers - Eric said he dimpled the flanges and dimpled the nutplate holes - others suggested to use dimpled nutplates. That was actually my first thought but when I priced them out they are listed at $2.40 each (K1100-06) at Aircraft Spruce compared to .51 cents (K1000-06) for the regular ones. That would add up to a big difference in cost.
I was steered toward Van's where the dimpled nutplate were listed at .58 cents each. That's a big difference from $2.40 at AS. I called AS and asked them about it and they confirmed that was the correct price due to the fact that they had run out of the surplus they had and the new supplier was a higher cost.
I ordered a bunch of dimpled nutplates from Van's at .58 cent each. So I wasn't able to actually mount any inspections covers but it's just dawned on me that I need to prime the flange rings first anyway.
