Keel bolts - summary

Well, after one month of fighting I got 3 keel bolts out.

Two of them went out pretty easy - they were in bad condition but oak layers through which they pass were not that thick.

Third one gave me lots of trouble due to deadwood through which it passed. Deterioration and rust expansion has caused it to really sit well, to the extent that it was impossible to remove it by simply pulinig it out inside the boat. Instead I was forced to take it in parts through keel opening pocket.

What would I do differently?

For such a nasty case I would try pulling it slower than I did, applying heat on the top part while pulling. This would make the metal expand and after cooling down hopefully the channel in oak and rust slug would get enlarged enough to enable extraction without breaking it.
To further increase odds I would maybe try cooling down the iron by applying -55 C spray in periods of pulling. Maybe it would yield metal more britle and prone to breaking but I don’t think the bolt will really go down to -55 degrees C. Worth trying but risky.

Then, if the bolt breaks upon pulling I would hammer it down again, as I did. It proved that the channel behind the bolt was already wide enough to accommodate the bolt. And yes, I would first drill pilot hole into the bolt’s core to inhibit mushroom effect inevitable with hard hammering.
Drilling through the bolt is tedious and very time consuming. Should I be forced to go this way all along I would build a jig for holding the drill steady and straight, with enough pressure to enable milling but without my assistance. Then I could leave it for few hours and come back to change the battery and replenish drilling oil.

The budget, not counting men-hours, became also stretched. That is mainly due to the lead being poured into keel pockets instead of being hammered in. That closed the option of drilling and tapping the lead plug and extraction with hydraulic jacks. Instead I had to melt it away - investing in new tools (which is cool but costs) and several bottles of gases.

So how do I proceed from here?

I’m considering enlarging keel bolts to 20mm metric. That would give me more options in steel rods which, in Europe, are manufactured mostly in 18, 20, 22mm etc. To get the same, 3/4 inch diameter I am limited to tool steel (silver steel) which comes in 19mm diameter - with very tight tolerances. That makes it costly.
Besides - oak in keel bolt channels is deteriorated by iron sickness. Drilling it out to 20mm diameter will expose fresh(er) wood and rusting of new keel bolts will proceed slower - at least I hope.
The only question is how long will it take to re-drill iron casted ballast keel.

I’m meeting my machinist expert this week so then we will decide how to proceed.

For lead plugs I’ve already decided to cast them into properly-sized bricks which then will be hammered into keel pockets and faired with epoxy for smoothing-up the surface. I don’t want to melt them to extract keel bolts next time!