Countersinking F/G Wing Tips

I went to countersink the #6 holes in the wing tip edge to accept the dimpled edge of wing skin for attachment with #6 screws.

The white gel coat cracks/splinters off well outside of the circumference of the countersink. Is there a trick to get good clean countersink for these holes? Funny that I did not have this problem when countersinking for my platenut attach rivets but these #6 holes are little ragged around the edge.

Jim
RV9A

I just did my R. wing tip last week and it did the same thing, I just took the CS bit and turned by hand a couple of turns. using # 8 screw

Expensive But....

AveryTool sells Permagrit countersink bits in various sizes for $22 each. You can use a regular CS bit on raw Epoxy like the cowl, but not the Polyester Gelcoated Tips as you discovered.

I used a shaped stone grinding bits on a Dremel

To countersink the nutplate holes in my wing tips with good results. I got the idea from somebody's site.

You can see pictures at my Builder's log:

http://www.mykitlog.com/users/displ...k&project=211&category=1860&log=110645&row=26