Tue Sep 27 2011

Countersinking step plates

This evening, I decided to countersink the step plates. Because these plates are somewhat bent to fit the curve of the fuselage, each hole needs to be countersunk individually by creeping up on the correct depth. This means many adjustments to do these 18 holes. There are a few holes which are too close to the weld to use a countersink cage, though.

...so I disassembled one of my countersinks to get just the shaft out of it.

Then, very carefully, countersink a little at a time hoping not to go too deep. It worked out pretty well. I had one hole maybe .001 or .002 too deep, but I was pretty happy with the results.

After several hours, I had both steps countersunk. Unfortunately on the left step, I wasn't paying attention to what I was doing at the beginning, and I countersunk several holes on the backside of the plate. Fortunately the depth wasn't set too deep at that time, but these holes did get enlarged somewhat. I ordered some 1/64 inch oversize rivets to use, but I'm not sure I'm even going to do that. I think they'll be fine with the regular rivets. After all, this heavy duty steel plate gets riveted to the side skin which is only .025 inch thick. I'm pretty sure any failure will be either the rivets in shear or more likely, the skin tearing out...and it would take a pretty severe overload on the step for that to happen.