After drilling holes to size in rudder assembly. The holes need to be countersunk to allow for the skin dimples. Problem here is that the wedge is thin and the hole will enlarge as it is counter sunk. My way of dealing with this problem was to drill the same size hole in the table top as the rivet hole in the wedge. Then I would move each hole over the drilled hole and countersink. The hole in the table would keep the pilot of the countersink tool from wondering around. And that kept the countersink in the wedge from chattering.
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