How can I straighten out my wood

Three Typical Movements

Longitudinal movement in normal wood is negligible. When going from green to dry, movement along the grain averages less than 0.1 percent – a 10′ piece of green wood shrinks about 1⁄8″ along its length. This movement is so small it has almost no impact on our woodworking techniques. If, however, the hardwood is juvenile wood (less than 20 years from the tree’s center) the shrinkage can be upward of 2 percent or some 20 times greater.

Radial movement is shrinkage that occurs as you move outward from the center of the tree. In flat-sawn lumber, radial movement affects thickness. This shrinkage is intermediate to the other two kinds of movement and is generally, in North American species, stated to be between 4 percent and 6 percent. On a flat-cut, 2″-thick piece of hardwood, movement could be as much as 1⁄8″ in thickness.

The third movement, and the one that is most substantial, is tangential movement. This is movement across the grain and should always be considered when building projects. Wood movement across the grain, again based on North American species, can be from a low of 6 percent to a high of around 12 percent. A flat-sawn 6″-wide board could move up to 3⁄4″ from the green to the dry stage. As you can see, tangential movement is nearly double that of radial movement.