Miter joints — so simple in theory and execution — often end up less than perfect. Here are a few tips to help you avoid relying on caulking or filler to finish them off.
Backcut When you think about it, the only part of the miter that has to meet is the outside, visible, edge. Anything behind that is not that essential. So by backcutting the joint, you can insure the corners meet while not worrying about the rest. You can either set up your saw to cut more off the inside of the cut, or pare it down with a utility knife after making your 45 degree cut.
Burnish Even if you’ve got a seemingly perfect joint, time and settling may give you a gap. If the gap is quite small, you can burnish it to close it up. Just roll the shaft of a screwdriver down one side of the joint, bending the wood fibers into the joint, and then do the other side. You’ll lose a little sharpness to the edge, but over all, it will look much better.
Cut a patch It happens to the best of us. Sometimes it’s tough to fit the piece in place to mark off the cut, or it’s a tough measurement to make accurately on your own, so the piece ends up a quarter inch or more too short! One way to avoid this is to initially cut long, and then gradually shave it down till it fits perfectly. But if you do end up short, and you can’t use that piece anywhere else, don’t rely on filler to close the gap. Depending on the location and how you’re finishing the wood, there’s another way. Leave the saw set up as it was and cut a small piece of the stock to fill the gap. Carefully glued in, this can make the gap disappear.