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SEMIJim 07-12-2012 11:03 PM

Drilling A 5/8" Hole In The Hull?
 
I'm going to be installing a Blue Sea CableClam 1001 in Abracadabra's stern this weekend. The model 1001 has a 0.63" (16mm) opening, which is approximately 5/8". That's smaller than my smallest hole saw, but way too big for a twist bit. What do y'all suggest? I was wondering if a Forstner bit would work well on fiberglass?

Thanks,
Jim

overbored 07-13-2012 12:02 AM

Re: Drilling A 5/8" Hole In The Hull?
 
buy a hole saw the forstner bit might get ugly

xymotic 07-13-2012 12:33 AM

Re: Drilling A 5/8" Hole In The Hull?
 
you could probably get away with a spade bit, but same caveat as above. do you really want to risk a $200 repair because you saved $10 on a hole saw?

sea_hunter 07-13-2012 04:54 AM

Hole saw. Epoxy inside of hole then redrill to final size.

LinekinBayCD 07-13-2012 06:21 AM

Re: Drilling A 5/8" Hole In The Hull?
 
Quote:

Originally Posted by sea_hunter (Post 895849)
Hole saw. Epoxy inside of hole then redrill to final size.

+1

Drill 3/4 ", fill hole with epoxy, then redrill 5/8".

SEMIJim 07-13-2012 08:10 AM

Re: Drilling A 5/8" Hole In The Hull?
 
Do they make holes saws that small? I assumed that, since I have two sets, and neither has a hole saw that small, that they didn't. But I'll stop by the local big box stores tonight, on the way home, and check.

As for the epoxy-filling: Not necessary. Abracadabra's hull is not cored.

*Hmph*... spade bit... Could work... if I was careful.

Obviously this is going to require more thought and research.

Thanks for the follow-ups!

Jim

Ulladh 07-13-2012 09:32 AM

Re: Drilling A 5/8" Hole In The Hull?
 
If you use a spade bit, only use a new one for a sharper outer edge, light pressure and don't go all the way, then finish from the other side.

Wear a face mask to protect from fiberglass dust.

Reef33 07-13-2012 09:59 AM

Re: Drilling A 5/8" Hole In The Hull?
 
I don't understand why you can't just use a 5/8" twist bit such as this one (scroll down and select "5/8"):
DEWALT Metal | Find Tools and Accessories

Forstner bits are for drilling flat bottom holes and auger bits are much less stable than a standard twist bit. Spade bit would work, but again, harder to control than a standard twist bit. I agree with drilling part way then finishing from the other side for a neat edge. 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.

Captainmeme 07-13-2012 10:05 AM

Re: Drilling A 5/8" Hole In The Hull?
 
Whats wrong with a twist bit? Pretty sure one can purchase a 5/8 bit that has a shank turned down to 3/8.

SEMIJim 07-13-2012 10:07 AM

Re: Drilling A 5/8" Hole In The Hull?
 
Quote:

Originally Posted by Reef33 (Post 895899)
I don't understand why you can't just use a 5/8" twist bit ...

I'm concerned about tear-out on the inside, and I don't believe I can get a drill in there to relieve the inside outer edge, first.

Quote:

Originally Posted by Reef33 (Post 895899)
Forstner bits are for drilling flat bottom holes and auger bits are much less stable than a standard twist bit.

These things I know. But, sometimes, tools can be used in ways other than that for which they were intended.

Quote:

Originally Posted by Reef33 (Post 895899)
But, I'm not an expert in drilling holes in boats, just wood.

I'm not an expert in drilling holes in either, but I do know this: Fibreglass is "chippy," or "flaky." For anything other than very small holes, it can be difficult to drill cleanly.

Jim


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