Thursday, January 13, 2011

The Finger Joint

I did not at first understand the importance of the finger joint in glued laminated timber (glulam) … to me they were just some `necessary evil’.  After all – don’t we picture in our mind the end of a glulam beam where the horizontally placed laminations are betrayed, with the glue (face-to-face) joints between?  However, without the finger joint – there would be no glulam altogether.   The deal is this: we can only make glulam beams as long as the individual laminations.  So, if we want a beam that is 50 ft long – we need 50-ft long lams. Easy. NO!  Well, yes with the finger joint.  Without it we would be searching for sawn lumber pieces 50 ft long each, continuous.  We don’t find lumber pieces that long.  in fact, if we go shopping for lumber input for glulam beams we will probably find it offered in lengths not over 16 ft.  Longer lengths are available, but they will cost.  In fact, the preferred sources of laminating stock will probably be `random lengths’ up to 16 ft.  Herein comes the beauty (actually importance!) of the finger joint.  The finger joint is used to join, end to end, individual wood pieces, into much longer laminating pieces.  If we want to manufacture a beam that is 50 ft long, we will finger joint pieces of various lengths into continuous pieces of 50 ft each, and then laminate (glue them face to face with one another).  The ability to `finger joint’ our input lumber allows us to use input material of, loosely speaking, `any’ lengths.  And if suppliers are given the liberty to cut the lamination stock into the best lengths for them, they will come available to the (glulam) manufacturer more affordably.

Pictured is a finger joint in one of the glulam beams at the Fireside Grill in town.  It is noticeable as two different color woods happened to be joined.  (Most of the other finger joints in the beams at the `Fireside' are far less noticeable.)

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