Drilling out keel bolt advice.

[BAD ORCA]

Originally Posted by Yojimbo

RE: Core drilling. Checked with my rental company- their 1" core bit is 16" deep and a rental unit might be a cheaper route. 2 points to consider- lead is much softer than concrete so the friction could cause melting- I think with patience and a slow progression it would work. 2nd- you mentioned a 1" diameter bit. Don't know your bolt diameter [7/8" ?] but I would give more than a 1/8" tolerance. If the bit chewed into a SS keel bolt you'd have a real problem with work hardening of the SS bolt.

Good to know. I didnt think about the possibility of renting. If my test with the coring bit goes well, maybe i dont buy a bit and just rent the drill and bit if i end up needing to do this. I will have to check around to see who rents them. Thanks.

My bolt is 0.75" dia. I was thinking i dont want the bit to be too big because it might start getting sloppy on the hole if it starts drifting too much. I guess it doesnt matter though as long i get the old bolt out because it would be backfilled with epoxy when the new bolt was installed.

I figured the old bolt would be a sacrificial pilot/guide for the hole saw or coring bit. The hole saw or coring bit would not be used with a guide bit but instead would use the old bolt as a guide. If the original bolt gets damaged im good with that as its being replaced anyways.

[deblen]

A final idea.
Can you leave the old bolts in place & install new bolts beside them?


As for anchoring new bolts-I don't think I would trust drilling oversize hole & using epoxy,melted lead,etc to hold bolts in keel.
I think(IMHO),using a cross nut/barrel nut,as I suggested earlier,would be safer. Of course,if you installed new bolts in new holes,you could thread the new holes.
Just opinion on my part.
Cheers/Len

[Bowdrie]

Be aware that no matter the shape/size of the teeth, you have to be very careful to withdraw the tool and clear the swarf from the teeth.
Sliding a hole saw over a bolt can work fine, but there is no place for the removed material to go.
An 1/8 > ~3/16ths is about the best you can do before the teeth clog up.
Once the teeth clog any further rotation only produces heat.
The old-time lubricant for drilling lead is Kerosene and it works quite well.
Some will try to sell you some special/magic stuff at 10 times the price, it'll work only marginally better at best, but it will probably smell nicer.

[BAD ORCA]

Originally Posted by deblen

A final idea.
Can you leave the old bolts in place & install new bolts beside them?


As for anchoring new bolts-I don't think I would trust drilling oversize hole & using epoxy,melted lead,etc to hold bolts in keel.
I think(IMHO),using a cross nut/barrel nut,as I suggested earlier,would be safer. Of course,if you installed new bolts in new holes,you could thread the new holes.
Just opinion on my part.
Cheers/Len

Thanks Len, yes for every bolt thats in my keel i can except the very first, forward bolt. This one is not reachable with the drill/tapping machine. If i have to sister in any new bolts for any of the others, the local guy that does this drills, taps and threads in new bolts into the lead keel to 14" depth. The only one that would be epoxied in is the very front bolt, but its secured from the bottom with washer and nut so epoxy is just to keep it centered in the new hole really and to fill the excess space.

[BAD ORCA]

Originally Posted by Bowdrie

Be aware that no matter the shape/size of the teeth, you have to be very careful to withdraw the tool and clear the swarf from the teeth.
Sliding a hole saw over a bolt can work fine, but there is no place for the removed material to go.
An 1/8 > ~3/16ths is about the best you can do before the teeth clog up.
Once the teeth clog any further rotation only produces heat.
The old-time lubricant for drilling lead is Kerosene and it works quite well.
Some will try to sell you some special/magic stuff at 10 times the price, it'll work only marginally better at best, but it will probably smell nicer.

Thank you. Yeah if i end up having to do this repair im expecting it to take pretty much an entire day just to drill the hole. Good to know on the kerosene, i have some here at work. I'll use it on my test holes.

[Yojimbo]

As you probably know SS work hardens when drilled. At a certain temperature is changes granular structure and becomes "impossible" to drill. Slow drill rpms, lots of coolant and plenty of force [vs speed] along with the right drill bits are your only chance and its a very slim one at that. Once a SS bolt work hardens you're SOL. 40 years of professional metal fabrication experience and I wouldn't accept the job for any amount of money. Core drill the bolt.

[BAD ORCA]

Originally Posted by Yojimbo

As you probably know SS work hardens when drilled. At a certain temperature is changes granular structure and becomes "impossible" to drill. Slow drill rpms, lots of coolant and plenty of force [vs speed] along with the right drill bits are your only chance and its a very slim one at that. Once a SS bolt work hardens you're SOL. 40 years of professional metal fabrication experience and I wouldn't accept the job for any amount of money. Core drill the bolt.

Good to know. that explains why i have so much trouble drilling any stainless fixtures on my boat. I think im overheating it.

I have definately decided 100% im not going to attempt to try and drill the actual bolt itself, just the lead surrounding it so i think this will not affect me.

[wholybee]

Originally Posted by Bowdrie

Be aware that no matter the shape/size of the teeth, you have to be very careful to withdraw the tool and clear the swarf from the teeth.
Sliding a hole saw over a bolt can work fine, but there is no place for the removed material to go.
An 1/8 > ~3/16ths is about the best you can do before the teeth clog up.
Once the teeth clog any further rotation only produces heat.
The old-time lubricant for drilling lead is Kerosene and it works quite well.
Some will try to sell you some special/magic stuff at 10 times the price, it'll work only marginally better at best, but it will probably smell nicer.

I would size the hole such that I could fit a vacuum hose, over the bolt and into the hole. Drill 1/8", remove the holesaw, vacuum, repeat.

[deblen]

May be helpful: https://www.cruisersforum.com/forums...lts-73976.html


https://forum.woodenboat.com/forum/b...6-#post7357627

[misssherry]

Have you taken the nut off of the suspect bolt? It is not uncommon for crevice corrosion to occur under the nut and not affect the lower part of the keel bolt. This scenario would be caused by stagnate bilge water instead of water coming up from the keel/hull joint. If the corrosion is limited to the top of the bolt, that section can be cut off and connected to a short threaded rod with a 316 ss coupler.

[BAD ORCA]

Originally Posted by misssherry

Have you taken the nut off of the suspect bolt? It is not uncommon for crevice corrosion to occur under the nut and not affect the lower part of the keel bolt. This scenario would be caused by stagnate bilge water instead of water coming up from the keel/hull joint. If the corrosion is limited to the top of the bolt, that section can be cut off and connected to a short threaded rod with a 316 ss coupler.

No not yet. I did clean it up from the top with a wire wheel brush but only have seen the top of the bolt/nut. Unfortunately that keel bolt sits in a little bilge compartment and was sitting in salt water that leaked in from a seacock in the bow for god knows how many years. The nut and top of the bolt are moderately corroded. The nut will likely have to be cut off.

Luckily i have room around the bolt in the bilge area to cut into to get a nut on deeper on the bolt if thats the case. On my boat they filled the bilge in with a special mixture like a thick gelcoat that was supposed to absorb impact loads in case of a grounding. At least thats how it was explained to me. I can easily cut into this material with a router if i have to remove some to get deeper access to better threads.

Fingers crossed this is all that will be required.

[misssherry]

Get a large socket on the nut and use a socket wrench extension that is long enough to clear the bilge obstructions. Use a breaker bar to remove the nut and inspect the bolt. Don't be surprised if the nut turns easily or the bolt breaks. I did this with several suspect bolts with the boat in the water. One nut at a time, of course!

[AKA-None]

Originally Posted by Yojimbo

RE: Core drilling. Checked with my rental company- their 1" core bit is 16" deep and a rental unit might be a cheaper route. 2 points to consider- lead is much softer than concrete so the friction could cause melting- I think with patience and a slow progression it would work. 2nd- you mentioned a 1" diameter bit. Don't know your bolt diameter [7/8" ?] but I would give more than a 1/8" tolerance. If the bit chewed into a SS keel bolt you'd have a real problem with work hardening of the SS bolt.

For soft metal like lead drill very slowly just like yojimbo mentioned

[AKA-None]

Originally Posted by BAD ORCA

Thanks for that. I think stainless would absolutely drive be insane. I would probably end up selling the boat and getting an RV.

I like others here have both
Don’t think one is necessarily cheaper than the other

[b.needalman]

Use a set of high quality metal bits. The drills have to be harder than what it is cutting. For stainless, use low drill speed and not too much pressure. Use cutting oil on the drill bit. Clear the hole frequently by pulling the drill partially our. Keep the hole wet with cutting oil. IF it smokes, it's getting too hot. Start with a small diameter and work up to larger sizes. Slow and careful does it. If stainless gets hot it will harden and then you will have more trouble.

Hone your skill on hardware from the junk box for practice.

PS This is the kind of thing that might be best done by a professional. The boat will turn upside down if the keel takes leave of the boat, with dangerous consequences to you and your crew.