Cutting holes - what type of drill bit/saw?

flapbreaker

Just wondering if there is a preferred hole saw/drill bit for cutting 2" holes for my navman fuel meter?

These look too toothy for gelcoat.

Sneaks · Posted: Wed Jan 04, 2006 12:40 pm Post subject:

I had occasion to drill a few large holes. I covered the (w)hole area with blue masking tape which was thoroughly pressed down and then used precisely the same hole saw you picture above, albeit with a gentle touch. Worked fine, clean edge drilling from the gel coat side.

Don

Captains Cat · Posted: Wed Jan 04, 2006 12:41 pm Post subject:

I used one just like that to cut a hole for my ST8000 Raymarine Autopilot in the dash of Captain's Choice. Just tilt it a little to the side until it starts and then you're home free...except for all the glass dust... Shocked

Charlie

Rabidfish · Posted: Wed Jan 04, 2006 3:03 pm Post subject:

All good ideas...

You may also want to start with just the pilot drill. Leave the "hole saw" off untill your pilot has gone through, then add the "holesaw" to make the hole. This will keep you from abruptly "biting" into the gel when the saw touches.

Also, Is the hole not 2 1/8" ?

Alyssa Jean · Posted: Wed Jan 04, 2006 5:00 pm Post subject:

I just installed two Navmans and used a hole saw that looks similar to what you have pictured but it has a 1/4 in pilot and centering drill that sticks out about 1/4 " farther than the circular saw. Worked just great.

B~C · Posted: Wed Jan 04, 2006 5:52 pm Post subject:

Just make sure you use enough lubricant before drilling any holes in the boat.....see David or Pat for the proper lubricant

Sea Wolf · Posted: Wed Jan 04, 2006 7:13 pm Post subject:

Flapbreaakaer-

Those inserts for the plastic head that holds the pilot drill do look a little "toothy", but they generally work out ok. When the saw section first contacts the fiberglass, it will "grab" a bit at first, so a steady hand and tight grip on the drill will help, as will a layer or two of masking tape to ease the entry and prevent some very small chipping.

They do make single sized hole saws where each circle size is a heavy steel metal bell shaped piece with slightly smaller teeth that are somewhat more suitable for drilling in harder subtances, and as such would have less chance to chatter, but you can do it with the ones pictured. The heavier ones don't dull as fast, however, if you have several holes to drill.

Be sure to provide for catching the fiberglass dust on both sides of the bulkhead wall, as it is nasty, itchy stuff that doesn't always vacuum up cooperatively, and a PITA in the cushions and carpets.

As for getting "lubricated" properly to "calm" one's neves and "enjoy" "shooting" holes, a half a bottle of Jack Daniels and a Roto-Zip saw will allow you to get really creative with the cutout shape and size. You can always claim your were also looking to "ventilate" the v-berth a bit. Bottoms up, engage tool, all ahead emergency speed!!!

The first hole's the hardest!

Joe.

Mr. Fisherman · Posted: Wed Jan 04, 2006 8:47 pm Post subject: STOP!

STOP!

Do not cut a 2" hole for that Navman fuel flow meter gauge!
Read the instructions.... I believe it should be 1 7/8" and it makes all the difference in the world. I had an existing 2" hole from the tach on my last motor and thought I was in business, wrong. There was just enough extra hole (1/8") to allow the gauge and the ring to slip right through. It was after this discovery that I got to make an 1 7/8" hole centered on a 2" hole for a mounting face. Fun fun fun.... Measure twice, drill once.

And another trick I learned with drilling holes into gel coat is to start the cut in reverse then go ahead and cut it.

I hope this helps....

Moxieabs · Posted: Wed Jan 04, 2006 9:17 pm Post subject:

The starting out in reverse definitely stops the chipping out of the gel coat past the true border of the intended opening. I leave it in reverse until fully through the gel coat, then forward through the fiberglass itself. Makes for a clean cut. The same works when just drilling small holes with a drill bit.

tpbrady · Posted: Wed Jan 04, 2006 9:18 pm Post subject:

Ditto on the starting the cut in reverse. It scores the gelcoat and minimizes cracking.

flapbreaker · Posted: Wed Jan 04, 2006 9:45 pm Post subject:

THanks for all the input. Hopefully I would of read the directions before I drilled as I was just guessing at the 2" size but thanks for the heads up. I do have a bad habit of reading directions after the fact. Smile

rogerbum · Posted: Wed Jan 04, 2006 10:46 pm Post subject:

In addition to the measure twice, drill/cut once rule, I always use the

"If you drink, don't drill!" rule.... Cocktail

Alyssa Jean · Posted: Thu Jan 05, 2006 10:05 am Post subject:

The Navman 3100 does take a 2" hole. At least the two I just installed did. The face which is square overlaps the hole by 1/2 in all around.

B~C · Posted: Thu Jan 05, 2006 10:42 am Post subject:

When in doubt, drill a hole in a piece of scrap wood and see how the gadget fits. The first hole is always the worst