Remove the hinge and clean and de-burr the drilled holes on each hinge half. Reinstall the hinge on the fairing using clecos in every other hole. This will guide the countersink bit and keep it from elongating the holes in the fairing. Countersink all the holes in the fairing. Rivet the hinge to the fairing, using a hand squeezer. Reinsert the hinge pin.
