HELP -- I need to drill a 1 1/8" hole in fiberglass

[Raz]

Originally Posted by Bob Miller

I have several well used Greenlee punches and warn others that they will punch a decent hole in molded fiberglass only if they are SHARP.

Any that have punched much metal get dulled tend to crack or craze molded fiberglass. For that reason I don't use mine on fiberglass.

Thanks for the tip. So far so good. Raz

[rabbit]

So you skate that 3/8" twist bit all over the place getting a pilot hole for the Greenlee arbor? I love you guys but I'd go with a plain old high speed hole saw and ease the pilot bit thru so the perimeter teeth don't catch. Helps to get the peimeter kerf even all the way round also as thin glass doesn't provide the best bearing for the pilot. The sheet metal step bit ain't bad neither if you got a big one. Got a router. Drill da hole in a piece of 1/2" or 3/4" ply, get it stuck on with some full coverage 2-sided tape, chuck a top pilot router bit in the router, plunge carefully in the middle of plywood donut, trace it out. Dust mask if you feel inclined; eye protection (hood or goggles) whether you do or not., On second thought, maybe you should leave that to me and my 35 yrs. of rattin out various openings by this fine old, time-honored light-industrial nastiness.


jack

[djtriceflt]

Originally Posted by Jim Bennett

This would work nice and quick, but there would be a bit of fraying on the sides of the hole. You would get a bonus second hole too, maybe for an access hatch on the other side. * * *





* * * Please kids, do not try this at home, this is a job for a professional.




All kidding aside, the hole saw is the way to go. As long as it is sharp, it will work fine. Start slow until you get a good bite. Use a bit of sandpaper to smooth out the glass shards on the edge of the hole when done too.

No rattail files? How about this?

[Ice-breaker]

I second the use of the fine toothed hole saw with sharp teeth. Couple of things that could help you ensure a better quality finished product:

1. Drill a small pilot hole entirely through the fiberglass before you begin. Use a regular drill bit and go to a size slightly smaller than the pilot drill on the hole saw.
2. If the fiberglass is accessible from both sides, start your hole saw on one side and go partway through the fiberglass. Then complete the hole from the opposite side of the fiberglass.
3. Stand back and admire your work and tell yourself that you are great. Take a picture of your work and post it on Fiberglassrv.com so that others can admire it as well.

cheers

[rabbit]

Never used a 90mm recoilless rifle as a rattail file. It would make a great mole eradicater for your back yard plus the bonus of backblast for leaf blowing. Pay attention to your loads for the shottygun or you'll get a speaker grille rather than a single hole.

jack

[Crackedegg]

I would use a forstner bit available at any home builder supply.

[Ron in BC]

You've gotten lots of excellent advice from those suggesting using a hole saw. I've done countless holes in glass with hole saws.

As others also mentioned, a wood block can help. I take a wood block and drill a hole with the hole saw, then drill a pilot hole in the glass, align them and clamp the block to the glass. (I have heavily taped them in place when clamping wasn't an option) With the hole saw held captive sideways in the wood block it becomes an effective guide to keep the saw from making an oversize hole if you wobble while hand drilling the hole.

It's always take a deep breath time when drilling holes in your shiny pride and joy but after the first few you get used to it.

Ron

[Thomas G.]

Originally Posted by Ron in BC

I've done countless holes in glass with hole saws.
Ron

I thought you literally meant glass. Reminds me of my uncle who decided to cut a 4" diameter hole in his basement window to vent a dryer. Six panes of glass later, he went with an aluminum plate with a hole in it.

[rabbit]

Ron's idea for a circumferential fence or enclosure of wood around the hole saw is a variation of a router template. Elaborate but better than a nasty gash in the gelcoat when the holesaw skates.

jack

[rabbit]

Beware of the central chip knife in a Forstner. It's meant to work in wood. It can wedge in glass and pull that tiny center spur to the side tearing out the pilot hole. Similar problem with multispurs.

jack

[Thomas G.]

Originally Posted by rabbit

Beware of the central chip knife in a Forstner. It's meant to work in wood. It can wedge in glass and pull that tiny center spur to the side tearing out the pilot hole. Similar problem with multispurs.

jack

I agree. A Forstner bit can bite in an do some nasty damage.