<html> Terry Farrell wrote: <blockquote type=cite class=cite cite>I have heard/read this many times, so I suppose it is true. But, intuitively, it makes no sense to me. If you drill a hole in a piece of wood and expose it to high humidity, the wood will swell - and swell much more across the grain (perpendicular to the grain direction) than with the grain. So why doesn't the hole tend to close a bit - on the two sides of the whole where the tangents are parallel to the wood grain.</blockquote> Because the whole piece of wood swells, and the hole becomes larger along with the piece of wood.  As I wrote in my last post, imagine the plug of wood which used to be in the hole.  The hole behaves the same as the plug of wood that was taken out. Do the hole and rod test.   Just pick a small piece of maple or something, soak it in water for a while,  then drill a hole in it with a spare drill.  After drilling, put the drill back in the hole, then dry the wood in the oven!  That drill will be really nasty tight in the hole!  You'll have to soak the wood again to get it out. There are some exceptions to this behavior: 1. In some situations the surface fiber swelling in the hole exceeds the change in shape of the wood.  Key balance holes are examples of this, where high humidity sometimes tightens the fit.  The wood thickness is small, and the wood fibers are large and sometimes made of more reactive wood. 2. Cross-laminated wood is more dimensionally stable, and the surface fibers will again have more affect on the hole size than the dimensional changes of the wood.  This is what happens in pinblocks. 3. If the hole was made by compression of the fibers instead of by drilling and removing wood (like with a nail) then the grip on the nail is tighter during humid times.  All surface fiber effect, no hole to swell. Don Mannino RPT </html>