Dealing with wood defects
In woodworkers' dreams, all wood looks like the boards we see in cutting diagrams: flat and straight with parallel edges and not a single knot or inconsistency. In reality, though, wood is far from perfect. Even the best grades often suffer from one or more of the defects shown in these drawings.
The best way to deal with lumber defects is, of course, to avoid questionable boards in the first place. But if a board has great grain, is the only one available that suits your needs, or carries a bargain price, don't reject it just because of a few problems. Use the following tricks to get the most from less-than-perfect lumber.
Bow: A board that rocks from end to end when laid on one face.
Salvage a bowed board by crosscutting it into shorter sections, matching the lengths of pieces to the curve of the board.
Use areas that are too bowed to produce flat stock to test setups or finishes. You may be able to create small parts, such as cleats or spacers, from the bowed pieces.
Crook: A board that rocks from end to end when laid on one edge.
How you straighten the edge of a crooked board depends on the severity of the defect. If the crook is mild, run the concave edge over your jointer to straighten it. Use caution to prevent the leading end from catching on the outfeed table.
For boards with severe crook, options exist. You can crosscut the board into shorter pieces, then joint each, as discussed above. You also can rip off the crooked edge at the tablesaw using a long carrier board, as shown in photo above. Or snap a straight line on the board, cut it with a handheld circular saw, then joint the edge smooth.
Cup: A board that rocks from edge to edge when laid on one face.
Rip a wide, cupped board into narrow flat sections, as shown in Photo B. Rip each piece slightly wider than you need, then rerip or joint the edges square to the face. You even can glue these sections back together to create a wide board.
Transform mildly cupped lumber into flat, thinner boards. First, joint the concave face flat, and then plane the other face parallel.
Twist: A board that rests on opposite diagonal corners when laid on one face.
A severely twisted board is difficult to save. You may salvage short pieces, though, by using a combination of the methods previously described.
Checks and shakes: Checks are cracks across the growth rings. Shakes are cracks between the rings.
These cracks occur at the ends of boards, so you may simply cut off the bad areas. But don’t be too hasty. Good narrow pieces often exist on either side of a check.
Shakes, because of their orientation, usually have to be cut off. Be leery of boards with excessive shake. This may be a result of the board simply being dropped on one end, but shakes also can be a sign of improper drying.
Knots: These are remnants of branches.
If they’re tightly held in the wood, knots usually pose just appearance problems. Use these boards in inconspicuous places where the knots won’t show. Loose knots, on the other hand, may fall out or be pulled free by cutting bits and blades. Cut out and discard areas with loose knots.
Written by: David Stone
Illustrations: Mike Mittermeier
Photographs: Marty Baldwin