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Old 01-01-2012, 13:53   #16
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Re: Drilling lead keel for bolts

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Originally Posted by minaret View Post
In my opinion, starts and stops are the most likely part of the cut to bind. Therefore this is bad advice. Much safer to make the whole cut with as few starts and stops as possible. Lead cuts like butter, easy to drill in especially with an auger bit to help prevent clogging. The big concern here is that few ballast keels are pure lead, how much iron is in there? I've drilled holes in ballast keels that went like butter, and others that did not. A 1/2" hole through 12" of lead should be a cakewalk. Try drilling straight and not binding when you're using a 3' extension and drilling in pig iron. A drilling jig becomes necessary. This should be a simple job. Definitely wouldn't use lags in lead, ever. Forstner bit to drill a counterbore for the fasteners is the way to go, then fair over with epoxy.
To prevent clogging you can use a wax, bar soap, solvent, kerosene or even a spray on teflon.
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Old 03-01-2012, 13:34   #17
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Re: Drilling lead keel for bolts

Quote:
Originally Posted by minaret View Post
In my opinion, starts and stops are the most likely part of the cut to bind. Therefore this is bad advice. Much safer to make the whole cut with as few starts and stops as possible. Lead cuts like butter, easy to drill in especially with an auger bit to help prevent clogging. The big concern here is that few ballast keels are pure lead, how much iron is in there? I've drilled holes in ballast keels that went like butter, and others that did not. A 1/2" hole through 12" of lead should be a cakewalk. Try drilling straight and not binding when you're using a 3' extension and drilling in pig iron. A drilling jig becomes necessary. This should be a simple job. Definitely wouldn't use lags in lead, ever. Forstner bit to drill a counterbore for the fasteners is the way to go, then fair over with epoxy.
Sorry minaret, I disagree with you this time. (Don't often do that)
In my experience, which includes a number of these jobs, its the lead peelings (swath)working up the drill bit which binds first. Not the cutting face. Therefore, lifting the tool often while the drill is decelerating, breaks the swath free from the cutting face point.
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Old 03-01-2012, 14:05   #18
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Re: Drilling lead keel for bolts

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Originally Posted by Blue Stocking View Post
Sorry minaret, I disagree with you this time. (Don't often do that)
In my experience, which includes a number of these jobs, its the lead peelings (swath)working up the drill bit which binds first. Not the cutting face. Therefore, lifting the tool often while the drill is decelerating, breaks the swath free from the cutting face point.
I agree with that, but pulling back on the bit and letting it slow down for a few seconds is NOT the same as starting and stopping. Coming to a full stop and restarting is where the sudden torque changes will get you off center and cause a bind. An auger bit really helps in regards to the peelings working up the bit, as that is what it's designed to do.
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Old 05-01-2012, 06:14   #19
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Re: Drilling lead keel for bolts

I'm considering the counterbore method - but, for the life of me, can't figure out how to accurately align the bolt holes with the side-bores - seems really easy to make a huge mess of bores and re-bores until you hit it right.
What is your advice on this?
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Old 05-01-2012, 07:36   #20
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Re: Drilling lead keel for bolts

Forget about side boring - you'll never line it up!
I'd suggest - if you have room - go rent a 3/4" mag drill, fabricate a heavy steel plate to mount the drill from - preferably something that can be clamped/wedged in place.
Drill out the tap hole, follow up with bolt size plus 1/64" over.
Use tap or lag bolts - preferably monel - install with epoxy to seal bolt threads and hole. Lag bolts will hold just fine in lead.
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Old 05-01-2012, 07:37   #21
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Re: Drilling lead keel for bolts

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Originally Posted by bweger View Post
I'm considering the counterbore method - but, for the life of me, can't figure out how to accurately align the bolt holes with the side-bores - seems really easy to make a huge mess of bores and re-bores until you hit it right.
What is your advice on this?
Skip the side bores. I've seen it done and it's a PITA for no good reason. I think it's a bad technique which hurts the integrity of the ballast keel right where it needs it most. Drill all the way through the bottom of the ballast keel, then use a forstner bit to provide a counter bore for the nuts and washer to sit in. It's tricky to perfectly align the counterbore since the forstner has no pilot, but doable. Once it's all bolted up fill the counterbores with epoxy and fair. It really helps if you've anticipated doing this job and asked the yard to block the boat extra high.
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Old 05-01-2012, 07:53   #22
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Re: Drilling lead keel for bolts

"Drill all the way through the bottom of the ballast keel"
Yeah, go ahead, if you get off by drilling holes for no reason!
Just lag the damn things in and be done with it!
Chances are the bolts you have in there now have been there for awhile?
Bolts deteriorate at the hull/ballast joint. A larger diameter would be more logical than bolting all the way through the keel!
If you're worried about it - go to a 5/8" bolt.
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Old 05-01-2012, 08:28   #23
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Re: Drilling lead keel for bolts

Geoduck has a point, I would reference a materials handbook, (sorry mine is at home right now). Once you get a certain thread length the combined thickness of the threads exceeds the strength of the bolt material.

In other words, the bolt will shear before it strips the threads. To get the exact ratio between cast lead, and the monel, stainless, bronze, or whatever the bolt material is, you need to look up the relative tensile strengths of the two materials. Even at ratios of 5 to 1, (monel = 66GPa, lead = 13GPa), a 1/2 inch bolt, (remember to subtract the thread depth) - Machine thread area ratio for 1/2-10 threads.

4.5 inches of lead, if torqued to fail, will break that bolt. Anything longer than that will just change the point of fail from the keel threads to the overly long and weaker bolt, that will then jam in the hole and require redrilling.
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Old 05-01-2012, 09:13   #24
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Re: Drilling lead keel for bolts

This info confirms the lag method for me.

I'm going to use 1/2 x 12 silicon bronze lags, in 2 pairs, installed thru a 1/4" bronze plate running athwart the bilge (set in an epoxy levelling bed)

Existing bolts are SS, but I always have a little water in bilge. Boat was in freshwater until I bought it for ocean about 6 years ago. They appear to be sound, but I've got a hairline crack on exterior at keel / hull joint and some cracking inside in the sole running lengthwise from each bolt. More cracking each year, especially this summer. I sail it pretty hard.
I also want to try removing the existing nuts and putting in much heftier washers than the ones in place.

Strength of bronze should be OK for torquing in, no?
Weight of keel is 700#
I could go with 5/8" lags, but would rather not, as I get horror stories about drilling lead.

Will a 3/8" tap hole work, then 9/16" for shaft part of screw?
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Old 05-01-2012, 09:52   #25
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That's another story. Usually, the "smile" on the keel joint shouldn't be a problem, but the cracks between keelbolts might indicate that you have other issues. Older boats have wood insidie the bilge area, for strength, and then covered with Fiberglas. If this wood gets soaked or rotten, it will have to be removed and depending on the size of the boat, about 1" of fiberglass should be applied instead. On the pic, rotten wood has been removed, the remaining wood is ok, so it was left in place and the rest was solid fiberglassed.
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Old 06-01-2012, 08:28   #26
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Re: Drilling lead keel for bolts

DONT START MIXING METALS!!!!
If your boat is fastened with stainless bolts/screws - stay with stainless.
If it is fastened with bronze - stay with bronze
etc,etc
Monel is your best choice if you can find it.
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Old 06-01-2012, 12:33   #27
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Re: Drilling lead keel for bolts

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Originally Posted by Geoduck View Post
DONT START MIXING METALS!!!!
If your boat is fastened with stainless bolts/screws - stay with stainless.
If it is fastened with bronze - stay with bronze
etc,etc
Monel is your best choice if you can find it.
Actually Aqualoy 22 (SS) is best>>> Keel Bolts and Fasteners
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