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Old 15-08-2011, 08:12   #1
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Cutting Holes in Fiberglass

Need to install a mushroom fitting and need to drill/cut a 1" hole . What is the best way to drill I have a 1 " flat wood bit or would I need a hole saw bit ?
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Old 15-08-2011, 08:14   #2
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Re: Cutting hole in fiberglass

I would go with the hole saw.
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Old 15-08-2011, 08:15   #3
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Re: Cutting hole in fiberglass

Use a hole saw. The flat wood bit would not work.
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Old 15-08-2011, 08:35   #4
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Re: Cutting Hole in Fiberglass

One inch hole I have done both ways doesn't really matter, hole saw takes ten seconds longer but a little prettier
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Old 15-08-2011, 08:51   #5
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Re: Cutting Hole in Fiberglass

Depends a bit (no pun intended) on the thickness of the fiberglass but both should work. Go with the flat wood bit as you already have it. I would drill from both sides rather than just punching through from one side.

Of course, if you need a "reason" to buy a hole saw, this is as good as any!
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Old 15-08-2011, 08:56   #6
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Re: Cutting Hole in Fiberglass

Use a shotgun lol
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Old 15-08-2011, 11:30   #7
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Re: Cutting Hole in Fiberglass

Forstner bit is best, hole saw is ok, spade bit sucks. Each will give you an okay finish if wielded with expert skill. A ten year old girl couldn't mess it up with a Forstner bit.
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Old 15-08-2011, 11:40   #8
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Re: Cutting Hole in Fiberglass

The paddle bit will work. Just make sure it's sharp and go slow. If you can get to the back side, once the tip is through, run it in from the back to get a clean surface on the inside. A hole saw would be better but why spend $ on a mandrel and bit if you'll never use it again. Maybe borrow one.
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Old 15-08-2011, 12:18   #9
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Re: Cutting Hole in Fiberglass

The hole saw will do the best job. If you use a shopvac to keep the sawdust from choking the teeth it will also keep the work surface and the tool cooler.
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Old 15-08-2011, 12:22   #10
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Re: Cutting Hole in Fiberglass

dont forget to epoxy your cut edges so water wont get into the fiberglass
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Old 15-08-2011, 12:35   #11
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Re: Cutting Hole in Fiberglass

you can also use a smaller drill bit to drill holes in a circle, then force the drill sideways enlarging the hole. once you get a hole, file it smooth on the edges using a coarse round file or a wood rasp file. Many ways to make holes.
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Old 15-08-2011, 12:55   #12
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Re: Cutting Hole in Fiberglass

Better still, use a BORMAX Centre Drill Forstner (if you can find one) as it is then less likely to wonder when starting the hole. Not cheap, so you might want to do as most of the others suggest, a hole saw from both ends if possible.
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Old 15-08-2011, 12:59   #13
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Re: Cutting Hole in Fiberglass

How much does a 1" hole saw cost for Christ's sake. Buy a damned hole saw, drill for a few minutes and be done with it.

Fiberglass dulls tools quickly. Can't believe a flat bit drill would drill more than a few fractions of an inch before it was too dull to drill a marshmallow. Forstner bit, Please!!!! These bits make nice clean holes but don't drill easily/quickly except in a drill press. They also seem to get dull real quick.
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Old 15-08-2011, 13:07   #14
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Re: Cutting Hole in Fiberglass

Invest in a good quality hole cutting set. I invested in a carbide tipped set last year & found it to be invaluable around the boat.
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Old 15-08-2011, 14:29   #15
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Re: Cutting Hole in Fiberglass

reading this thread has brought to my curiosity how could you make these holes air-tight? For instance, if you're running a pipe or whatever it is you sailors might want to run through the hole, what could be used to keep water from coming in through the sides of the hole?
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