We have installed six all thread 316 stainless 1/2 inch rods into the keel.
When the keel was cast long ago, iron rods were embedded in the lead. These have been cut off at the mating surface and the new bolts are offset a few inches from the originals.
We initially tried using a high speed steel bit to drill into the lead. No good. The shavings are not ejected and quickly bind up the bit. It will either break or become immovable. We did it both ways.
Next we tried a forstner bit. This worked well. It cuts a clean hole and the short walls of the bit allow it to be frequently removed to clean the hole. Unfortunately we did not have one with sufficient length.
While we were waiting on a special long shaft bit we ordered from Rockler, we tried a new sharp ship auger bit. (love the name)
While I expected it to be too aggressive and bind up, it just pulled out this beautiful long apple peel of lead. You can drill about a half to three quarters of an inch then pull the bit to clean it off.
Once we figured this out, the holes were quickly done. We drilled the primary holes for the bolts and then from the side, we cut in a set of holes we worked into slots to fit in the washers and nuts.
Here are some low quality phone photos of the work...
|The 16 inch long Ship Auger bit is visible in the drill at the top of the photo.|
|Here the doubled 316 fender washers and nut are visible in the slot.|
|Our first ugly hole.|
|In this photo the lead is laid on its side to facilitate drilling. Here, 5 of the six bolts are installed.|