How to Cope Miters for a Perfect Fit
A coped joint looks better than a mitered joint. Here are some pointers on how to do it right. Remember: life is hard—learn how to cope!
Why Not Miter?
Cutting both pieces of trim at 45 degrees to create a 90 degree corner makes sense, at least in theory. But in the real world, two walls rarely form a perfect 90-degree angle, so getting two miters to meet tight and right is challenging or impossible. And even if you get it tight, the joint will probably open as wood naturally shrinks or swells. Coped corners take these elements out of play.
The Basic Procedure
Since the most commonly coped molding is baseboard, we’ll use that as our example. Begin by butting the side that won’t be coped into the corner and nail the baseboard in place. Now you’re ready to cope the other baseboard. There are four basic steps
Step 1. Make a miter cut
The 45-degree cut will—through the magic of geometry—provide a perfect profile to guide your coping cut. When you make the miter cut, leave the baseboard a couple inches too long. You can cut it to final length after the coping is done.
2. Cut the Cope
Follow the profile created by the miter cut. Relief cuts at tight turns allow waste to fall away and your saw to make turns more easily. You can make straight cuts faster and better with a miter saw (more on that later).
3. Fine-Tune the Cope
Your coping cut doesn’t have to be perfect. Even the best trim carpenters use files, rasps and sand-paper to clean up their cope cuts. Tight curves, for example, are almost impossible to cut with a coping saw. But a small file rounds them easily.
4. Test the Fit
Keep a scrap of the trim handy so you can check the fit as you fine-tune the cope. With really complex profiles, you may have to check and fine-tune the fit a dozen times before you get it right.
Start Out Straight Up
Baseboard often tilts inward at the bottom because of the drywall’s tapered edge. And that makes coping tricky. To avoid trouble, make sure the baseboard sits square to the floor. If it tilts, remove it and drive a screw into the framing near the floor. Leave the screw head slightly proud so it holds the baseboard away from the wall. Then check again with your square. You may have to turn the screw in or out a little to get the baseboard to stand straight up.
Coping Saw Setup
If you’re using your grandpa’s coping saw—well, actually any coping saw—do three things:
- Replace the blade if it’s rusted or worn. Blades can have anywhere from 10 to 20 teeth per inch; use one with at least 15.
- Make sure the teeth point at the handle; coping saws are designed to cut on the pull stroke (though some carpenters use them backward).
- Make sure the blade has proper tension. Adjust the tension by rotating the handle clockwise or counterclockwise.
Cope Straight With a Miter Saw
Cut the “straightaway” with a miter saw for a faster, straighter cope. Turn the molding upside down, set your saw at least 5 degrees to the right and cut straight down until you hit the curvy part. Some pros even nibble away at curved profiles with a miter saw.
Coping cuts often create thin, pointy tips on the trim. Support those tips with your finger as you cut, file or sand to prevent them from splintering off.
Cope With a Jigsaw
A narrow, fine-tooth blade cuts curves much faster than a coping saw. It’s also a fast way to wreck your cope, so practice on scraps before making real cuts. Before you try this, turn off the orbital action on the saw.
Sculpt the Cope
Tools that match the curves of a profile make coping faster and better. On complex profiles, you could try a file, rasp, rotary tool or dowel wrapped with sandpaper—or all of the above.
Cope With a Belt Sander
With simple ranch-style moldings, you may not need a coping saw at all. Cut the straight section with a miter saw, then cope the curve with the rounded nose of a belt sander. Belt sanders also help out on some styles of crown molding.