Join Date: Feb 2004
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Buy a hole saw for the drill. Simply nothing else works better and you can now buy the lower-end hole saws for less then $12 a set.
When using them, drill/saw most of the way through the GRP, then around to the other side, thread the centre biyt into the pilot hole and finish sawing form the other side, this gives you clean edges on both sides without any gelcoat popping off the edges.