drilling holes in gunnel - which type of hole saw

[mwardncsu]

I am going to be installing some Scotty flush-mount rod holders tomorrow and need to drill several 1.25" holes for them. I went to Home Depot to get a new, fresh, sharp hole saw for this. I picked up the normal kind, but I also saw one that does not have teeth, but rather an abrasive "grit" (I assume industrial diamond or the like) and its marked for drilling tile, stone, etc, but also fiberglass. It does have a pilot bit (also with the abrasive material)

I was wondering if this would be a better option than the traditional wood / metal hole saw? It would basically abrade its way through vs. cutting (and perhaps chipping)?

I know the "normal" ones are used by many - anyone ever used this other type - pros/cons?

thanks...

[EODContender]

A regular hole saw will work. Run it forward until the pilot bit gets through, then put the drill in reverse when the teeth of the hole saw bit make contact. This will cut the gel coat without chipping it. Once you see fiberglass showing, put the drill back in the forward gear and continue drilling through as normal.

[seabob4]

Place two layers of masking tape over the area of the holes you want to cut. Use a standard toothed hole saw. The masking tape will prevent "chipping" of the gel.

[triumphrick]

Be careful that the pilot bit doesn't grab and pull the holesaw into the gelcoat...EOD's method is a good one, but I always use a separate pilot bit in another cordless drill. I drop it down a size below the pilot bit of the holesaw and use reverse. I have yet to try those abrasive bits..if you do let us know how they worked....

[bumster]

The abrasive bit is fine if you're going thru solid glass. It does not play well with coring material especially wood. two layers of tape and drilling a pilot hole are excellent ideas

[1bandit]

Always drill a hole through a scrap piece of plywood at the angle you will be drilling the hole first. Then clamp or tape the plywood over the gunwale and use it to guide the hole saw and protect the gel coat. You don't have to use the pilot bit while using the plywood guide.

[mwardncsu]

thanks all for the quick responses - this is a "plumb" hole in the gunnel, but the wood "angle jig" is a great tip if you're are drilling at an angle. These are going into a a Sea Hunt BX24 - I am pretty sure there is no coring material there. I figured the abrasive bit would elevate the need to go back and chamfer the edges of the hole and be much less likely to chip the gel coat, although I know the backwards technique is well tried and proven. I'll flip a coin in the morning and decide which bit to use, and which to take back....

[TTaxi]

No need for the slow abrasive bit but get a bi-metal hole saw with pilot bit mandrel , and definitely start with the backwards tip you are aware of. Take it very slooow coming out the bottom if not using blocks, or if there's room, switch to underneath when seeing the hole saw just start to bite through.

[number9]

Damn,
What did some of us and others do in the days drills didn't reverse to get a good hole in FRP or were they all chipped up? Must say at one time it was difficult enough to get a good hole in wood even in shop class unless you paid high $ for your bits/saws. Progress is a wonderful thing.
beans...

[camobob]

I used a standard bit and masking tape on my 19' Sea Hunt - no coring materials, no issues.
Take a good long look at everything below where you are planning to drill. I came real close to a swim ladder bolt with one rod holder and another had to be angled to clear the transom.

[aubv]

If room permits, clamp or block a piece of plywood to the bottom of the area where the hole is going to go. This will help prevent blow out. Drilling from the bottom after starting from the top can lead to a slightly offset hole wall ,even with the pilot hole. Hold the drill firmly and don't run the drill at high speed or you run the risk of the saw grabbing the fiberglass and twisting violently.

[Capttater]

For model.. I tried to use some cheap whole saws ($10 for the kit) and it would drill about 1 hole and be shot and the battery on my drill would be dead too.
I went and bought an American made Rigid that cost about $30 with the pilot bit and I drilled 3-4 in the same time and on the same battery.
You don't want an abrassive bit unless it's full glass which I'd doubt. The other tips above work well. Don't forget to epoxy the exposed coring.

[PRO-BLU]

Make sure you put the hole in the rite place so the end of the rod holder dont hit the inside of the fiberglass side before you cut anything. The like the other guy said, buy an expensive hole saw bit, the one's they sell seperate. Dewalt bits work perfect, if you buy those cheap ones where you get one of every size you will never get the hole drilled. Dewalt bits will have fiberglass and wood flying everywhere, those cheap bits just sit there and smoke.

[tb714usr]

Don't want to hijack the thread, but do you guys have any different suggestions for drilling holes for 45 degree holders with no access to the bottom?

[mwardncsu]

thanks to all for the suggestions & reassurance. I was mounting the "flush mount" Scotty round mounts for their adjustable rod holders (well, actually Cabelas version of the "QuickDraw' holders). I used a double layer of masking tape, ran the pilot bit in reverse to get started, then forward, and then reverse again when the hole saw portion was about to make contact, and then forward again once through the gel coat. The gunnels were I was drilling had a 1/2" or so fiberglass backing glued to the underside of the gunnel, so I was drilling about 1.25" or 1.5" deep.

The only issue I ran into was that on a couple of the holes I must not have had then perfectly plumb and the mount did not want to sit fully flush to the gunnel - so, I pulled out my Dremel tool with a small sanding drum bit on it and eased the inside of the hole to widen it down to the inside so allow the mount to sit flush.

These Scotty mounts also had to "registration" holes that needed to be drilled - those went more or less without issue as well - I did use a chamfer bit to ease the edges of those holes after drilling.