Drilling out keel bolts?

[NLOM1]

Hi

Anybody have any experience of drilling out keel bolts? My cast iron keel has been sawn off. I've got just 3 bolts to deal with but there are not shifting and am considering drilling them out and am looking for tips on how best to proceed.

thanks

norman

 

[Peterduck]

I can think of two ways to go about this. Which one you choose will depend on the resources at your diposal.
The first is to drill a small pilot hole from each end along the axis of the bolt as close to the centre of the bolt as you can. You'll obviously mark the centre with a centre-punch to begin with. Open out and deepen the hole progressively, until the whole bolt has been removed. You may have to go slightly oversize, as the bolt is obviously rusted, with rust being compressed into the walls of the original hole. If this rust is not removed, it could continue to give trouble in the future.
The second method is to acquire a length of steel tubing whose inner diameter will go over the ends of the bolt which are accessible. Cut saw-teeth in one end and temper if possible. Drill a hole transversely through the other end of the tube to take a tommy-bar. Use as a hole saw over the end of the bolt, removing the wood & rust mixture from around the bolt. This is clearly going to take a lot of sweat and tears. I wish you luck.
Peter.

 

[Lakesailor]

Having made your hole saw, couldn't you hire a large, slow drill from the tool hire shop?
Something like the Kango hammer type drills, but without the hammer action.

 

[stevesales]

Can we have a bit more info on dimensions and what material(s) the remains of thse bolts are stuck in ?

 

[NLOM1]

oops.....more info.....

the steel bolts are in wood, presumably oak and then pitched pine.dead wood. We don't know what the boat is or how old. 22ft gaff rig. There is heavy rust staining in the wood around the bolts. The embedded bolt length is approx 20 ins. 2 of the them are resisting all pressure, I reckon the other has 'collapsed ' on itself after a couple of hits with the top section sunk about 1.5 ins and offset.

 

[stevesales]

OK. Diameter of the bolts ?
Can you still see the hex head ?
Do you have an ordinary electric drill, preferably mains not battery ?
Don't suppose you can take a photo ??

 

[Peterduck]

I was trying to keep it simple. Once you start employing large power tools, the need for a high-specification steel tube becomes important, so that it doesn't just fold up when the torque is applied. Then the driving end has to be fashioned and welded to the tube. Also consider the vertical space under the boat. While it may be enough to accommodate a tube of the required length, will it be enough to take a large power drill as well? A hole drilled upwards will clear the cuttings automatically, which a down hole will be less prone to do. In this case it will be necessary to approach from both ends of the hole.
Peter.

 

[stevesales]

Depending on the bolt diameter the simplest solution IMHO is to drill and tap them approximately down their long axis, screw in a length of all thread and pull them out using a nut and big washer on the end of a suitable length of scaffold pipe or similar.
I have used this technique on wooden frame buildings with big old iron bolts and the force you can apply is enormous.
The advantage is that , apart from a cheapo or borrowed tap, there's no expense involved and you can work in pretty confined spaces. All you need is enough headroom for the length of the bolt.
You're also left with a hole the size of the old bolt rather than a much bigger one. It would be a pretty smart home made hole saw that would go through nearly 2 feet of oak and pitch pine, you've got to offset alternate teeth to get external and internal clearance and you'd have to use a high carbon steel tube (GOK where from) heat it red hot + quench then take it to a straw temper to cut oak. Pitch pine is even worse - it produces tarry chippings that cook onto cutter teeth and in no time your drill is red hot + blunt.
What about a trade in for a nice fibreglass boat with integral keel?

 

[huldah]

Interesting to see the suggestion about making a cutter to drill out a rusted in bolt. I had something similar, removing rusted hexagon headed steel screws, holding a cutlass bearing in place, in oak. I made up a prototype cutter by brazing bits of all-hard saw blade onto the end of a tube. (High speed steel retains it's hardness when heated). Time was short, so when it broke I was unable to make an improved model. I am, however, sure it can be done.

So I used a piece of thick walled tube, rammed it over the pointed end of the screw and drilled it out. Rather disanointed with the results, as the hole left in the oak was larger than intended. On the other side the screw had completely rusted away, so replacement was easy. However, if a bolt is rusted to a point, so that a centre punch cannot be used, drilling down through a tube will countersink the end. This would leave all the other options, as suggested on the forum, open.

I often wonder if it would have been better to have only removed about two inches of the screw, and run a smaller diameter bronze screw up the side. The idea being to securely hold the bearing whilst nature removed the screw. A full sized bronze screw could then be fitted

Philip

 

[stevesales]

Yes you could certainly drive a piece if tight fitting tube over the end of the bolt to guide a drill onto it to give a centre point, nice idea.
I wonder about a good soaking in battery acid. Rust removers convert ferric oxide to phosphate which is insoluble in water but H2SO4 would convert it to ferous sulphate which is. Don't think it would significantly damage the oak but might take a few days to penetrate the length. With the rust converted to sludge it might simply be possible to drive the remains out. I still favout the pulling technique though cos I know it works.
I suppose the other possibility, re Huldah, is to ignore them if they don't leak and put in new bolts. If they eventually start to weep that can be dealt with.

 

[Plum]

Why remove them?

Why not just drill new holes between the old ones for new bolts as if it was a new build?

 

[stevesales]

Re: Why remove them?

Dads wot I suggested...