Rough-sawn lumber often needs to be squared up to construct everything from doors, trim, wall cladding, and flooring to tables, countertops and window shutters. Even if one face is left with its natural live-edge shape as a decorative accent, the opposite edge should be squared with straight, true corners if the board is to join correctly to any other workpiece. Avid woodworkers might use a jointer to square board edges, but a table saw can also get the job done.
1. Decide whether at least one long edge of your board is straight and flat. If it is, then align the straight edge with the table saw’s rip fence. Make sure the blade is set to 90-degrees, then push the workpiece into the blade to cut off the rough side, removing only enough material to straighten the board’s edge.
If neither edge of your workpiece is straight, you must create a straight edge using your table saw.
2. Select a scrap piece of 3/4-inch plywood that is 1- to 2-inches wider than the width of your board and is at least as long as your board. Make sure the plywood has one straight edge. This edge will ride against the table saw’s rip fence while the plywood serves as a sled for ripping the workpiece edge straight. (Ripping is cutting a board lengthwise in the same direction as the grain.)
3. Position the workpiece on the plywood sled so the edge to be ripped is facing the table saw blade, and the straight edge of the plywood is flush with the rip fence. Attach the board to the plywood sled using two wood screws located safely away from the blade.
4. Adjust the rip fence so that the sled/board combination will push through the blade, trimming off any defects while straightening the edge of workpiece.
5. While wearing safety glasses, make the cut and use a push stick to guide the material past the blade.
6. One edge of the board should now be perfectly straight. The workpiece can be flipped around to align the straight edge with the rip fence to square up the opposite side.
7. Repeat the process for all board faces that are out of square.
8. For short workpieces, the square ends of the boards can be aligned snugly against the table saw’s miter gauge and passed through the blade to square the edges. Long workpieces have a tendency to misalign when cross-cut with a table saw. Longer boards will get a more accurate cross-cut from a miter saw or a handheld circular saw guided by a Speed Square.
Editor's Note: Special Thanks to Randy and Caleb Stephenson for help with this article.