CS4-4 with 100-degree countersink

[ymc9]

I came to realize quite late that CS4-4 rivets are 120-degree ... Now it looks like I need to redo the roll bar . I'm also searching back in the KAI to find out where I might have used the wrong countersink bit in previous sections. It would have been much nicer if Section 5 had some clear information about it.

I have to say the KAI is quite misleading - in some places it explicitly calls out for a 120-degree countersink for CS4-4, and in other places it doesn't say anything. And I somehow assumed by default #30 holes are 100 degrees. Do you guys know the rationale behind it? Is the angle only critical in some locations?

 

[stigaro]

Ailerons also use CS4-4's on the end ribs, but dimpled not countersunk. I'm not sure if 120 degree dimple dies are available, but if they are, I didn't use them and my rivets sit a little proud.

 

[ymc9]

Ailerons also use CS4-4's on the end ribs, but dimpled not countersunk. I'm not sure if 120 degree dimple dies are available, but if they are, I didn't use them and my rivets sit a little proud.

I've been using only the bundled dimple dies from Cleaveland Tools (100-degree, I believe), and the rivets seem to sit pretty well. Dimples are not so accurate so maybe the angle doesn't matter too much?

 

[stigaro]

I've been using only the bundled dimple dies from Cleaveland Tools (100-degree, I believe), and the rivets seem to sit pretty well. Dimples are not so accurate so maybe the angle doesn't matter too much?

I was just looking at my ailerons last night and noticed them sitting a little proud in the dimples, but also in the countersunk hinge. I clearly didn't realize CS4-4 were 120 degrees in either location. I suspect the issue with using 100 degree countersinks is only aesthetic, not structural.

 

[bjdecker]

120° dimple dies are available from Cleaveland Tools (and Avery before that...)

120 Degree Dies For 1/8

120 Degree Dies For 1/8" Pop Rivets

cleavelandtool.com