There is a nice calculator here:
http://www.woodworkerssource.com/movement.php
One of the reasons I thought to post this today was because of a couple of postings I did recently about getting pretty accurate on the cheap. Here are a few salient points mentioned in the notes below the calculator:
Lets take the absolute low limits from the above - longitudinal shrinkage for KD lumber stored inside and say it is 1/4 of 0.1%. What does that mean in plain English? At a length of greater than 4", it is virtually impossible to have accuracy of a thousandth of an inch except for right at the instant you cut it. At over 5', claiming accuracy of a hundredth is iffy at best.
This is not an excuse for sloppy work. But it does make it difficult to justify the expense of some of the high tech measuring devices.
http://www.woodworkerssource.com/movement.php
One of the reasons I thought to post this today was because of a couple of postings I did recently about getting pretty accurate on the cheap. Here are a few salient points mentioned in the notes below the calculator:
Shrinkage green to ovendry: laboratory tests have been conducted for most commercial woods to measure how much the wood shrinks from the green to the ovendry condition. In this context, "green" refers to wood at or above the fiber saturation point. Shrinkage is greatest in the tangential direction (along the growth rings), ranging from about 6% to 12% with an average of 8%. Shrinkage in the radial direction (perpendicular to the growth rings) ranges from about 3% to 5% with an average of 4%. Shrinkage in the longitudinal direction is minimal, only about 0.1 %, and can generally be ignored for most furniture applications.
Keep in mind that the green to ovendry shrinkage values are maximum shrinkage values; kiln-dried wood that is stored indoors will only shrink perhaps one-fourth to one-half of the maximum amount.
Lets take the absolute low limits from the above - longitudinal shrinkage for KD lumber stored inside and say it is 1/4 of 0.1%. What does that mean in plain English? At a length of greater than 4", it is virtually impossible to have accuracy of a thousandth of an inch except for right at the instant you cut it. At over 5', claiming accuracy of a hundredth is iffy at best.
This is not an excuse for sloppy work. But it does make it difficult to justify the expense of some of the high tech measuring devices.