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Machine countersink depth question

A

atalla

Well Known Member
Hello all.
I'll cut right to it.
.32 E702 Spar
4 AD426 rivets to the E705 root rib

When counter sinking the spar as per the directions in section 5 of the manual I am not able to get the rivet to sit flush without the hole being enlarged. Will this rivet squish in after setting? I don't want to go any deeper and cost me a spar see pictures.




Thoughts?
 
Rivets

In my experience, rivet heads will not smush down. If the machine head is proud to start, it will end up proud after riveting.
 
I see you work in the automotive industry. Are you sure your countersink is an aircraft one, not an automotive one? Different angles.
 
If you end up with a slightly proud factory head, you can always shave them down with a rivet shaver bit in your countersink cutter cage driven by your trusty 1800rpm drill (the fancy 20,000+ RPM pneumatic shavers are not necessary).
Tom.
 
If you are concerned about the csink moving around, make a backing plate from a piece of thick aluminum or hardwood and clamp it in place. Match drill to the pilot size and then countersink. Reuse the backer until it wears too much.
 
.032 can be machine countersunk but it is right on the edge. As mentioned, you must back your work with a pilot guide. Typically, you match drill, clamp, then countersink in the same operation. The structure provides the guide. You must get the head flush or it will sit proud. Rivet shaving is risky even with a high dollar shaver and there is no reason to go there.
It helps to lubricate the cutter.
Practice on some scrap to get your cutter set to the correct depth.
 
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