Wednesday, November 23, 2011

Wood Movement

One of the things I have wondered about is that several respected woodworkers have glued the side boards to the legs, a cross grain joint.  Because the side boards are so wide, shrinkage is a major issue, particularly here in Oregon where we have hot dry summers and cool wet winters.  According to the Woodweb calculator, and assuming the moisture content ranges from 7 to 14%, this could be as much as 5/32".  Perhaps extreme, but it convinces me to take shrinkage into account.

I have decided to deal with shrinkage by floating the torsion box on the legs.  I will glue and peg the bottom of the side boards to the legs and extend them 1/4" above the top of the legs.  The 6" transverse bearers will rest on a 6" ledger glued to the side boards, which will allow the sideboards to expand and contract freely without affecting the top.  This ledger also serves as a long stretcher and will keep the bench from racking.  As a result, my bench will be like the Nicholson plate in not having a long stretcher across the bottom.

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