Workshop Tip: Find the Length of Any Picture-Frame Molding
This simple bit of math helps me quickly figure out the right length for any mitered picture-frame molding, based on the art or mat that goes inside. I then use that overall length to set up a stop for mitering the ends on the tablesaw. Start with the length (or width) of the mat, add 1/16 in. for an easy fit, and then simply add twice the distance from the rabbet to the outside edge of the frame. This trick works because the miters are 45°, which means the distance from the rabbet to the edge of the frame is the same as the distance from the end of the rabbet to the point of the miter.
—Tom Richey, Davis, Calif.
Illustrations by Dan Thornton
From Fine Woodworking issue #275