Countersinking and deburring^2h

More countersinking and some deburring today.

No photos of the actual progress, it was mostly countersinking some more parts, plus deburring of other parts.

However, while reviewing the plans, I found the following note that the bottom rivet attaching the gear web must be flush inside. After checking with the F-7114 gusset I found that indeed it needs to be flush.

So, without doing any thinking (impulsivity at its best, "not so fast"!), I countersinked the F-704 part from the inside.

And then I realized, that it's not the F-704 that needs to be countersinked, but rather the F-7101 web! The countersink is not too deep, so I was considering upsizing the hole half-size for the NAS1242AD4 rivet. However, the issue is that the edge distance on the F-7101 is already too small, and I will need to countersink it, too!

Another alternative I considered was to manufacture a small conical washer to sit in the countersink. But again, given the small size of the countersink, it would be hard to make a washer.

Finally, I thought about just ignoring it, but then I got concerned that the "thin" countersinked F-7101 hole will bend into the countersink under the pressure of a rivet shop head being bucked. And then it dawned on me that I can dimple the F-7101 instead, and treat this joint as any other flush rivet joint (dimpled outside and countersinked structure under it)!

The F-7101 is quite thick, it is 0.063", but a test on a scrap piece showed that it dimples okay.

So I think I dodged this one. Moreover, it seems I will be able to put the AN426AD4 shop head on the inside, making it completely flush (which is desirable -- the F-7114 gusset sits flat to the gear attach web!). The outside shop head doesn't matter as it was supposed to be a universal head on the exterior anyway. I might go fancy and buck it with the universal set to make it a shop-made universal head.