DIYbanter - View Single Post - Accomodating movement on a 70"w by 42"l table top!?

Doug Miller

In article ,
says...

Now I'm confused. I always thought (maybe erroneously) that the
primary expansion was in the direction of the grain,not cross grain
and not uniformly in both directions. That would be, on the OP's
top, in the 42" direction, across the table. Have I got it backwards?

Yes, you do. Expansion along the grain is, for all practical purposes,
zero. The principal dimensional change with changing moisture content is
tangent to the growth rings; that is, in the width of a flatsawn board,
or in the thickness of a quartersawn board. Radial dimensional change
(perpendicular to the growth rings) is typically approximately half of
the tangential change.