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6561Re: Treenailing? WAS: Grain in joints and finishing questions

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  • albionwood
    Jul 1, 2006
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      --- In medievalsawdust@yahoogroups.com, "msgilliandurham"
      <msgilliandurham@...> wrote:
      > > I'm guessing from the context that "treenailing" is using some kind
      > of narrow pegs as if they were metal nails -- but could you
      > elaborate, please?

      Treenails are basically wooden nails. There really isn't much
      difference between pegs and treenails, except the latter sounds
      cooler. It's more the way they are used that's different: Treenailing
      implies (to me at least) fixing one board atop another, whereas
      pegging is a way to lock mortise and tenon joints together.

      Note well, however, that these terms aren't rigidly defined, so other
      writers may use them in different ways. (I think in boatbuilding a
      treenail means a peg with a head, like an unthreaded bolt, so it can't
      be pulled through a board. But what I know about boatbuilding
      wouldn't cloud your vision if it was in your eye, so...)

      > Elongated how, please?

      When pegging a wide, cross-grain mortise-and-tenon joint, you can
      elongate the peg holes in the tenon so that the tenoned board can move
      without opening up the joint. For example, a breadboard end might be
      fixed with three (or five) pegs. The center one is done the usual way
      (i.e. drawbored - the hole in the tenon is offset slightly toward the
      shoulder, relative to the holes in the mortise) so all movement is
      away from the center. The other holes (also drawbored) can be
      elongated slightly across the grain, so that the tabletop can shrink
      or swell without cracking.

      I don't think this was ordinarily done much in the MA because thick
      riven planks don't actually move that much, and because the pegs are
      flexible enough to accommodate some movement. But I wouldn't be
      surprised to see it on clamped-front chests or tabletops in the late MA.

      > Also, the book which started my thinking about this issue, says
      > that "when assembing a box or drawer [this is one where the grain of
      > all four sides is the same] turn the boards so tha annuual rings
      > curve out [...] The board's natural tendency to cup will keep the
      > corner joints tight at the edges."

      This is true only if the board is losing moisture and shrinking. The
      outside of a log shrinks more than the inside, so it cups opposite the
      curvature of the rings. It's also only true for plainsawn (flatsawn)
      lumber. Quartersawn lumber has little tendency to cup.

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