Cutting & Coping Crown Molding | THISisCarpentry

Raise your hand if you have ever cut what you thought was a perfect crown cope only to find out it was open on the top or bottom? I’m raising my hand, too!

There is a great deal of misunderstanding about how copes work: for many carpenters, pressured by the need to ‘get the job done,’ cope joints are mysterious puzzles they haven’t the time or the patience to solve. But if we understand what makes a coped joint work then every cope can fit perfectly on the first try.

This cope is open on the bottom because the preparatory miter was cut incorrectly! (Note: Click any image to enlarge)

I’ve heard all kinds of reasons why cope joints won’t close up tight: The framing sucked; the walls were out of square, the building was 200 years old, or most often, the sheetrocker was a slob. Sure, those are fair points to make, but cope joints solve nearly all those problems! To prove my point, I built a mockup corner with a moveable wall, which demonstrates conclusively that a proficient trim carpenter can overcome a lot of jobsite chaos.

Cope joints are fast and flexible

The mockup I designed in the previous video that Gary used proves that—with a slight adjustment—a cope joint will accommodate a corner that is 2 degrees out of square, and 2 degrees over a 12-ft. wall is 5 in. out of square.

A cope joint can still close tightly, even if the ceiling is out, too. This is why progressive carpenters who care about craftsmanship, as well as production finish carpentry crews, cope all inside corners. The joinery is tighter, and coping is faster than mitering. Cut a cope a little long and snap it in place—it will close up even tighter. And if you cut that square end a 1/16-in. short? No problem! A cope will cover all of it but the very bottom edge.

If you do cut miters for inside corners, each piece must be cut precisely the right angle and length. If a mitered molding is too long, the long point will bury itself in the drywall, making it impossible to mate the miter joint. Cut a miter too short—well, you all know what that means—cut a brand new piece.

Why copes work better

When we cut a 45-degree miter joint on baseboard and discover it doesn’t close because the walls aren’t square, there’s no choice but to re-cut the miter. However, that’s not the case with a cope joint.

If you look at the bottom of the base with a miter cut, you can easily visualize a 45-degree right triangle. Remember back to high school math: in a 45-degree right triangle, both sides are equal. So if the molding is 3/4-in. thick, then the base of the triangle must be 3/4-in. long. That means the miter cut is 3/4-in. deep from the long point at the back of the molding, to the short point at the front of the molding.

Now imagine a cope cut following that miter: the cope will be precisely 3/4-in. deep, exactly the thickness of the molding, and the joint will fit perfectly every time. At this point, I think it is important to stress what the word “cope” actually means: this isn’t a psychology class or a self-help book; in carpentry (and in life, too!) we don’t cope with molding, we cope to molding—we cut molding, shelving, countertops, decking, casing, and cabinets so that they fit to other surfaces or features. And that is a task of skill and beauty.

Sprung crown

Now let’s go back to the first sentence in this article: How many of us have cut a sprung crown miter and noticed that the cut was off? I mean, from just looking at the miter, not the joint. On baseboard, it’s easy to notice a poorly cut miter; on sprung crown, it’s tough to see if the cut is correct.

At presentations and carpentry clinics, I call this a shell game: can you spot the correct cut? Here we have three miter cuts all done at 45 degrees. To find out which cut is correct we need to measure each piece. With solid crown and baseboard, it’s easy to measure the right length of the miter—it needs to equal the thickness; with sprung crown, you need to know the ceiling projection in order to be able to measure the length of the miter cut. Remember to think of the ceiling projection as the thickness of the crown if it were solid.

Miter saw setup

So how do we make certain that our preparatory miter for a cope cut is perfect?

When I first started installing crown molding, I was taught to place the molding in position, “upside down and backwards,” in my miter saw, then rock it until it was bedded flat against the base of the saw and the fence, too! Then draw a line across the bottom of the crown (that’s the top when it’s upside down in your saw) marking the miter saw fence, and try to hold the crown at that line while cutting it. But there are two problems with that approach.

First, you shouldn’t attempt to position the crown so that it’s flat against the fence and the base of the saw. Focus only on the fence! If the crown molding is flat against the fence, you’ll be cutting it at the intended spring angle—the spring angle is the angle the molding ‘springs’ from the wall, and the fence represents the wall! You’ll also notice that with the crown flat against the wall or your miter saw fence, the shoulder at the ceiling should touch only on the very outer edge of the crown. That is the way well-designed crown should land—so that irregularities in the ceiling won’t prohibit the crown from contacting the ceiling.

Check out this video Gary did with still photos for his original Conquering Crown DVD:

The second problem with that old-fashioned approach is the pencil line. It’s really difficult to hold the molding right on the pencil line, and if you do, you have to lock your hand dangerously on the crown. And even then, if your saw blade is a little dull, or the material is dense hardwood, the molding will resist the blade, the blade will push down on the material, and the spring angle will change as you’re cutting the crown.

Holding the crown in position by hand does not work. And it’s dangerous.

Cutting on the flat isn’t the best solution either and introduces a host of other problems. If the crown is cupped—and most coved crown has at least a slight cup because that’s the nature of wood—it is almost impossible to get consistent cuts because the molding won’t lie flat on the base of the saw, which changes the position for each cut. Further, when I have to cut on the flat, I often have to use a crown chart or an angle finder, like the Bosch angle finder that provides miter and bevel settings for crown molding with any spring angle. For those reasons, I cut on the flat only when the crown is too large to cut in position. Plus, who wants to set miter and bevel angles to a tenth of a degree.

A simple crown stop

I like to use a crown stop for all my cuts, both for copes and outside miters. One setup covers everything. And I use a crown holder, too. Here’s a video that explains the saw setup, crown stop, and how to make a crown holder. Don’t just use the crown holder for the cope joints, it’s great for outside miters as well!

Like many finish carpenters, Gary Katz prefers to use a crown holder—a lesson he learned from David Collins, which works just fine for the majority of jobs. But if you’re working in a home with ceilings that aren’t anywhere near flat—bows and bellies and waves, then cut a 24-in. piece of crown with a cope on one end. Use that coped piece, along with a straight cut piece, to mark the drop of the crown in each corner—when those two pieces fit together tightly, you’ll know the drop is spot on!

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AUTHOR BIO

Bill Shaw studied mechanical engineering and spent a year in the corporate world before deciding it was not for him. During the next ten years Bill started and co-owned an auto repair shop and then worked as a cabinetmaker.

The cabinet shop manufactured flooring on cabinet-making equipment, which seemed very inefficient. Thinking there was a better way, Bill opened his own business, with a leased Weinig moulder, knife grinder, and a used straight-line rip saw. The next 20 years were spent manufacturing custom moulding. While delivering the moulding to the job sites, Bill would check in with the customers asking if there was anything else he could do. More than one customer answered by saying, “Yeah, why don’t you cope this stuff before you deliver it.”

With that goal in mind, Bill collaborated with his father-in-law, Martin Scott, a retired engineer/machinist, which led to the development of the Copemaster. Two years of field testing produced the first version, which won the prestigious Challenger’s Award at the 2002 International Woodworking Fair.

When not producing Version 2 of the Copemaster, Bill can be found with the love of his life—his wife Loure, and in the machine shop, wood shop, or out on his dirt bike (a 50-year passion, which started at age 18).