Working with wood screws

[Mark Rendelman hull 24]

This is an fyi I was watching this old house on tv today  and just learned after working with wood for over 60 years that drilling a pilot hole in your work piece not only makes it easer to start your screw but it will allow the screw to hold up 22% stronger and that I did not know  so for us as boat builders this is perk

  I guess this just goes to show you that your never to old to learn something new 

[Hirilonde]

A pilot hole should be the diameter of the shank of the screw, not including the threads. In really hard woods, maybe even a tad larger.  It not only makes puting in the screw easier, it reduces the compression the screw applies to the wood around it.  This reduces the chances of a split occuring and allows the threads to cut into the wood better. It also reduces fastener fatigue.  This is when screws damage the wood to the point they hold far less than they should/could.

[Reacher]

Also, the pilot hole should be a little shorter than the screw so that the threads at the tip bite into wood. I can’t remember the additional holding strength the tip provides, but it is significant and worth doing.

[Hirilonde]

49 minutes ago, Reacher said:

Also, the pilot hole should be a little shorter than the screw so that the threads at the tip bite into wood. I can’t remember the additional holding strength the tip provides, but it is significant and worth doing.

Or buy a tapered bit designed just for screws.

 

[Mark Rendelman hull 24]

Yea what I said

[Don Silsbe]

 But don‘t most of us use mainly sheet metal screws on our boats?  Come on.  Fess up.

[Hirilonde]

1 hour ago, Don Silsbe said:

 But don‘t most of us use mainly sheet metal screws on our boats?  Come on.  Fess up.

When I build a traditional plank on frame boat I use bronze wood screws with a frearson drive. I use my Fuller combination counter sink, clearance and pilot tapered bits adjusted to depth.

[Don Silsbe]

I used bronze Frearson drive screws for my gunwales & c/b cap, but all hardware attachment is with sheet metal screws.

[Reacher]

Yes to silicon bronze frearson drive wood screws with a combination pilot bit attachment for joining wood. (That's a mouthful for a simple little step.)

 

Yes to using some stainless sheet metal screws for deck fittings on the Core Sound to match metals or when cap heads are needed.

 

And don't forget to clear any sawdust from between the plank and the frame after the pilot hole is drilled.

[Designer]

Driving in a drywall or a self tapping screw with the modern cordless drill or driver is giving us all bad habits. Beside the obvious job of holding two parts together, the smooth shank of the wood screw allows you to draw the two parts together. The self tapping screw will thread its way into the work piece and thread its way into the main part leaving no way to draw them together without stripping one of the threads. If I am doing something quick and dirty like on the house and I can't be bothered getting the drill and drilling a clearance hole in the work piece, I will start the screw in the work piece and then hold it away from the house and run the screw all the way to the head and keep driving until I strip out the thread. I then put the work piece in place and drive it home. It can draw the work piece tight because there is no thread left.

 

The other important job of the wood screw is to carry sheer loads. In carvel planking the screw gauge is unusually large. Nevens' rules for wooden yacht construction calls for 2" #14 screws for 1" planking. The reason for this is for the sheer loads. because the wood is relatively soft we need lots of bearing area to prevent the hull from wracking under load. While that might not be of much interest the modern boat builder we can learn from it.

 

The Goejeon brothers came up with a clever way to spread the sheer loads in the wood for a self tapping screw when mounting hardware, yes it involves epoxy. If you are using a 1"# 8 screw,(I am ignoring the the thickness of the hardware in this example) drill a 3/8" hole 3/4" deep, fill hole with epoxy and hand drive the screw just snug. This increases the sheer carrying capacity and waterproofs the wood in one go. When using this method I wait as long as I can after filling the holes with epoxy before driving the screws because the epoxy sinks as it soaks into the wood the screw will displace some epoxy. Of course this can't used on vertical surfaces.

[Hirilonde]

4 hours ago, Reacher said:

Yes to silicon bronze frearson drive wood screws with a combination pilot bit attachment for joining wood. (That's a mouthful for a simple little step.)

 

LOL, yeah.  Was trying to condense what they do to a single sentence.  This is the set I have................https://hardwickandsons.com/products/w-l-fuller-8-countersink-drill-set