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Peter Follansbee and Mike Siemsen
have cleared up the mystery of the pinwheel-shaped wooden nails. The
pinwheel shape of the nails is caused by the shell or gimlet bit used to
make the hole. The long edges of the bit bite into the grain, tearing
it. When the peg is driven into the hole, it takes the shape of the
hole.
Siemsen demonstrated this process with a square peg. Follansbee (who took the photo above) uses more of an octagonal shape.
Shell bits are similar to spoon bits and aren’t used much anymore (you can read about them here on the Full Chisel
blog). I’ve used spoon bits in chairmaking and have noticed that they
do tend to tear at the end grain in a hole, but I’d never seen such
dramatic deformation in a peg. I use a lot of dry oak pegs when
drawboring and have noticed that in my work it’s the hole that tends to
deform instead of the peg. So I might start with a round hole that turns
into an octagon as the peg is driven in.
In any case, thanks to Peter and Mike for setting us all straight.
— Christopher Schwarz
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I am working on an old trunk that I found in an old barn, it has these wooden nails in it. I have never seen these before. They used them to attach the trim pieces onto the front of the box. They also were used to attach the bottom to the box. The rest of the box is held together with dovetailing. I am very excited to restore this trunk.
" …. noticed that in my work it’s the hole that tends to deform instead of the peg."
Sure, I cut a square peg then round and slightly taper the end. When I drive it into a round hole, it shows as a square peg. I use this primarily for breadboard ends.
More importantly, where on earth could we get those bits? Those are cool looking.