I just freed a stuck bolt in the rear nds eyelet on the '70s Galaxy I'm working on. I used a small drill bit and just kept going at it until I removed a lot of bolt ... then I could finally unscrew it with vise grips. Whew!
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I use the threaded Campy eyelet (without a nut) for the rear rack on my grocery getter. Every couple months I make sure those two m5 bolts are secure. I like that setup better than the necessity of a backing nut. Just seems "cleaner."