Finished all the deburring and dimpling on the rudder understructure. Everything was going so swell and then I got to the step where I match drill the counterbalance weight to the counterbalance rib and dimple the rib and countersink the weight. This went so smoothly last time. I must’ve let my guard down. The drilling went well. I deburred the hole and cleaned everything up to dimple these for the #10 screws which screw the weight to the rib. I thought this went well too but then I looked at one of the holes and their was a small radial crack extending from the hole halfway down the dimple. I should’ve quit here…but no…I decided to countersink the weight and in my frustration over the rib, I wasn’t focusing very well on the counterweight and ended up countersinking too deep. I read a few structural manuals and, apparently, radial cracks can be acceptable. However with the deep countersink, I’m sure the pressure the screw will put on it will cause the crack to propogate. It might not but the counterbalance rib and weight aren’t that expensive to replce so I’d rather just have piece of mind. The mistake I made with the dimple was very preventable and obviously so was the countersinking. Doh. I had turned the adjustable ram on the squeezer too many turns and it was squeezing so hard that the yoke flexed a little. I’m sure this must’ve been too much for the dimple. You live and you learn.

Not easy to see but you can tell the hole is a little distorted.

This is a little more focused.