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  Topic Review (Newest First)
07-14-2012 09:21 PM
Lost Parents
Re: Drilling A 5/8" Hole In The Hull?

just drilled

Just drilled a 1/2in hole through my side hull .
, used tape and a 1/2in hole saw and took it easy when just about through , no chipping or flaking in or out
07-14-2012 08:24 PM
Re: Drilling A 5/8" Hole In The Hull?

Use a spade bit. You only need one hole, they are cheap. They don't self feed like a twist drill, so it won't tear a big ugly hole. The point comes through well ahead of the cutting edge, so you can finish from the other side if you want and get an absolutely clean hole.

If you HAVE to use a twist drill. Do NOT drill a smaller pilot hole, that will guarantee a rip out when it grabs. Remove the rake from the drill bit, using a diamond file or stone. Hold the bit horizontal with your right hand and the point away from you. Rotate until the cutting edge on the left is also horizontal. Hold the stone or diamond file horizontal and stroke it towards you on the cutting edge until you create a small flat. Rotate the bit to the other edge and repeat. Now you have drill bit that works excellent in all plastics, copper, and soft aluminum.

Gary H. Lucas
07-13-2012 10:47 PM
Re: Drilling A 5/8" Hole In The Hull?

It turned out my local Home Depot did not have a 5/8" hole saw, but they did have a 6/8" one, and that's close enough

07-13-2012 06:44 PM
Re: Drilling A 5/8" Hole In The Hull?

Drill it to 1/2" first, then take a counterbore bit and chamfer the edges of the fiberglass to a depth of about 1/8". Now go back and drill it to the final size of 5/8". No chipouts!

And definitely coat the inside of the hole w/ epoxy (if it's cored).

Dave's rule: Don't EVER skimp on tools for a job that counts. You will more than make up the cost by not having to repair something that got buggered.
Or beating yourself up for not doing it right to begin w/.
07-13-2012 05:02 PM
Brent Swain
Re: Drilling A 5/8" Hole In The Hull?

5/8th twist drill bits are common , sometimes with a smaller shank ,in many tool supplies. A 1/4 inch pilot hole lets you drill from both sides, chewing up the ends of the hole less.
07-13-2012 02:46 PM
Re: Drilling A 5/8" Hole In The Hull?

those large twist bits never seem to leave a nice smooth round hole .

remember to champher/countersink the edge of the hole so the sealer can form a nice o ring.
07-13-2012 02:17 PM
Re: Drilling A 5/8" Hole In The Hull?

For what it is worth, I used a 1 & 1/8 Forstner bit to drill a hole in the wall of my cockpit for an autopilot outlet. I too was concerned about chipping and fracturing that you can get with a hole saw. The Forstner worked great, I just went slow and easy and kept everything square and drilled a very nice hole, no chips and no fiber strands.
07-13-2012 12:08 PM
Re: Drilling A 5/8" Hole In The Hull?

Well, since it turns out they do make hole saws small enough, that's the way I'll go. I've done that before and it's a process with which I am comfortable.

Thanks, everybody, for your input!

07-13-2012 11:36 AM
Skipper Jer
Re: Drilling A 5/8" Hole In The Hull?

From the drawing it looks like you have about 1/2 inch of covered area around the 5/8 drilled hole. So any chipping will be covered up by the deck ring.
07-13-2012 11:33 AM
Re: Drilling A 5/8" Hole In The Hull?

Originally Posted by Reef33 View Post
And I can't see drilling the wrong size hole and then repairing it to get the right size hole when you can just drill the right size hole to start with? But, I'm not an expert in drilling holes in boats, just wood.
The goal with the oversized hole then repairing it, is to provide a plug that eliminates the core where the hole is. Obviously in a non-cored hull it isn't as much an issue. I still prefer to do it though, since it allows you to do the final drilling into a surface that is a lot cleaner. Fiber threads can allow water transportation into the hull, though it's not necessary.

For a hole this size I would defiantly recommend a hole saw. Not just because it is easier to control, but it also helps control the amount of dust and itchy fibers. Forstner bits will work, as will spades, but they pulverize everything, and make a huge mess.
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