Drilling 1.06" - 1.125" Dia. Hole in Fiberglass?

[Dave S]

I am installing a Pinpoint 7520 consul mounted graph and need to drill a hole through my fiberglass dash for passing the power and transducer cables. Any ideas on the best way to do this. Have seen earlier posts suggesting a unibit (conical shaped stepped bit) which worked fine but costs $20 - $40/ bit. Hole saw will severely chip fiberglass gell coat. Any other suggestions on how one might make this hole which would avoid chipping the gell coat? Does someone make graumets for covering up this large hole in ones dash?

[Jason]

I used a standard hole saw. It chipped, but very little. Then I put white silicone around the wire and in the hole. Then I installed a Perco Stainless Clam shell over where the wires came out. Looks great and is completely waterproof.

[Dave S.]

Jason: Can you tell me where you found the Perco Strainless Steel Clam Sheel Cover? Did you slit and drill the cover to fit the cables or do these covers come preslit with a hole in the center? Is the cover held in place by the adhession of the white silicon caulk or is the cover fastened with screws?

[Stan]

Dave,

Big Jon makes plastic feed through caps (available in 1 or two wire openings) that fit in a 1" hole. That is the minimum hole size, there is room to go larger. These make for a neat installation and can be removed (3 screws) in order to service or change electronics.

Have you tried using masking tape over the surface of the 'glass before using a hole saw? It would seem this might work.

Take Care

Stan

[Jason]

I have never tried masking tape, next time I will try it. As long as you turn the bit slowly it usually doesn't chip to bad.

The Perco clam shell cover, it actually looks like a clam shell. The wires come out of a hump in the plate. You don't have to cut anything. It has three small screws that hold it in place. I also use them on the back of my boat where the transducer wires go thru the transom. I like them because they make for a very neat and clean installation. I usually put silicone around the wires and then on the three screws before I put them in, that way everything is sealed. Make sure you wipe off any excess silicone. You can get them from almost any boat dealer.

[Grampa_Joe]

You certainly don't need a hole that big. I've put hundreds of holes in glass boats and this is my process.
Use masking tape to avoid scratching the gelcoat with spinning fiberglass. It also works well to sketch out where you are going to put things. I use forcner bits. You can buy them at any woodworking store. A Ø7/8 or Ø15/16 hole is adequate for a Pinpoint. Bigger holes than that, I usually go with the hole saw. Put a hole through a 2x4 first and make sure you can get all your wires through. Now, after you drill your holes for your wire cover screws, be sure to chamfer way more than you have to or you'll crack your gelcoat when you put in the screws. The chamfer has to be large enough that the screw itself doesn't even touch the gelcoat, only the fiberglass and/or wood underneath.
Joe Carlson

[forstner bit]

n/m

[REW]

The other postings are great - use masking tape - a slow drill speed and you won't have problems.

There is no need to use a cover for covering the larger hole that you might be drilling.

Use the depth finder mounting bracket --- or the mount that you might be using to mount your depth finder bracket to cover the hole.

If you are using the standard mounts - fine - just postion the depth finder exactly where you want it. Mark the holes.

If you are using a mount -- like a RAM, ultra mount, Johnny ray, or other - mount the depth finder mount to the accessory mount and position the depth finder exactly where you want it. Mark the holes.

In both of the above cases -- put down a layer of masking tape - before marking the holes.

Then drill the mounting holes for the depth finder mount or the accessory mounting bracket.

Now, look at how large the cables are -- not the head, but the cables. Determine where the best place for the cables to come out from under the dash to get to the depth finder power and transducer connections. Typically - the center back of the mount is the correct spot. Now, make a mark on the masking tape -- on the very edge of the depth finder mount where you want the cables to run. Typically a 1/4 or 5/16 inch hole will be large enough for the cables.

Remove the depth finder and or accessory mount.

In the area of the console or bow - which is under the area that will be covered by the depth finder mount -- and right next to the area that you want to run your cable -- or even use the extrem outer edge of the large hole to run your cables ---- drill the large hole required.
I generally like to drill the hole so that all of the hole is covered by the mount. Then I drill the 1/3 or 5/16 hole required for the cables. Then I use a file - to create a path for the cables to slip through. Often, if you let the edge of the hole extend bast the base of the mount about 1/8" of an inch, you can use a round file and gently file the hole to perfectly accomodate the cable. You can also use the file to very slightly round the top and bottom side of the hole, so that you don't cut the cables on any sharp corners.

Bottom line - when you are comple - you will have the depth finder mounted -- wiht a very small home - fully filled by cables directly behind and against the depth finder mount. Clean simple and neat.

Take care

REW

[Dave S.]

Thanks everyone for the helpful suggestions on drilling the hole for my Pinpoint 7520 locator. Picked up a hole saw and it made a nice hole. Got everything mounted last evening and it looks great!

[moose]

I'd use the hole saw but first scribe the circle with a devider. ( compass with two points ) might be tough to find but if you have a regular circle compass that a pencil clamps into, replace the pencil with a nail or wood screw with a point sharpened on the end.
Scribe the circle just ever so slightly larger than the hole saw. Scribe several times to get it somewhat deep. You also might want to drill small center hole and repaet same process on back side.