I think pretty much everyone knows that when installing new fittings on a cored boat we should first remove the core before filling the void with thickened epoxy and then re-drilling for the fastener(s).
There are a bunch of different ways to do this, but the set of Alfa Tools Forstner bits I just bought myself, while far from inexpensive, are the quickest, neatest, and generally best way I have found to make a suitable hole in the outer skin, and remove most of the core, without penetrating the inner skin.
Way better and more controllable than a hole saw.
Highly recommended.
Forstner bits are a joy to use overall. I haven’t touched my spade bits in ages. Lee valley have a good selection for Canadians out there and shipping is free.
Fiberglass is hard on Forstner bits. If you want them to last, you may want to drill the skin with a whole saw, then switch to the Forstner to remove the core
Hi Torten,
I guess, but I don’t do it that often, and the Forstener is so much better than a hole saw that I will just replace a bit that gets blunt.
With correct file &stone these can be sharpened in minutes. Creating more solid waste from an item with only a tiny part (edge) needing a little grind isn’t appropriate
Hi George,
That’s another option, although I think I’m right in saying that overheating of the tool steel from use in fibreglass may do for the bit and make it impossible to sharpen, but I don’t know that. Anyway, if it takes an edge, that’s what I will do, assuming it ever comes up, which with my usage frequency is, I think, unlikely.
Good idea— but I would rather use the cheapest Harbor Freight bits rather that high quality German ones.
I really like to drill the hole in the topdeck with a 8mm or larger bit and then ream out the rest with the dremel bit 115 using the hole as a guide. This leaves some topskin intact fixing the epoxy plug in place.
Hi Hugo,
Good point, I rake out some core around the hole too, for the same reason.