Posted by JLabaree on April 25, 2005 at 14:33:56 from 207.5.234.19 user JLabaree.
In Reply to: Mary Anne Design posted by John on April 25, 2005 at 00:35:07:
John,
Congratulations on good progress on the boat. Sounds as though you have things well in hand.
About those screws: silicon bronze screws are notoriously weak and susceptible to breaking, especially when driving into tough wood. However, they shouldn’t break so repeatedly that you can’t use an electric driver. My only thought is to make sure the pilot hole you have drilled is large enough. It needs only be slightly smaller than the diameter of the screw shaft (its “core” if you will). Indeed, I have been told that 10% smaller is sufficient, since a screw’s effectiveness is really limited to its teeth. In really tough wood, slightly larger pilot holes are acceptable.
Certainly, the screw shouldn’t be overly difficult to drive (not only is that a pain, but it weakens the screw). I have included a link to an excellent reference published by the US Coast Guard about wooden boat specifications. You will find a good discussion about wood screws. I’m probably nuts telling this to an engineer, but I thought I’d risk making a fool of myself in case it helps shed some light on your project.
Are you using tapered drill bits? Fuller makes a nice set specifically designed for wood screws of various sizes. Jamestown sells them. I use my Makita 9.6v cordless drill as a driver. It has a clutch, which can be adjusted to prevent driving the screw in too deep and two speeds – fast for drill bits, slower for driving screws. That works quite well.
Sorry the plank-splitting exercise didn’t work out, but I can well understand. I am certainly not in a hurry to plank a boat out of oak and your experience partly explains why!
Good luck!
- Jonathan