Crown Molding: Cope Or Miter?

      Either can work - craftsmen share opinions and tips. April 14, 2005

Question
When working with prefinished crown moldings, I generally have always cut 45s on my inside miters rather than coped them. My reasons are that some of the crowns can be quite intricate, large, and out of hardwood and if you can do a 45 for an inside corner in less time it's faster. This sometimes means back beveling with the belt sander and adjusting angles etc. which at times leaves me wondering if this is the best way. I was wondering what you guys are doing and why you think it's better?

Forum Responses
(Cabinet and Millwork Installation Forum)
From contributor A:
I would definitely miter those corners. Coping take forever - by the time you cut the general pattern, then file, etc. you could've been finished with a mitered corner. There is some adjustment to get things to line up but it's still faster than coping and you can actually get a glue joint that will hold.



From contributor B:
Iím with contributor A on this. Coping may sound more old world and craftsman like, but unless it's specíd, time is money. I find that an experienced man with a couple samples can check a fit and call down to the cut man to make a degree or hair or so change in miter, for a good fit. I find that I only need to take a block plane and touch-up for back bevel rarely this way. And really who wants to cope a piece of 9-1/4" crown with dental and extra beading in it, unless it's necessary.


From contributor C:
I'm of the opinion that coping is appropriate for common moldings but not for furniture, and kitchen cabinets are pretty close to furniture. I don't like to back bevel or face fit my work. Find the bisection of your angles and let your saw do the fitting. Your best chance of joints staying together is getting maximum glue surface. I will also add glue blocks behind outside corners and with some crowns there is a rabbet at the top allowing a v-block to be glued to inside corners. With the trend towards larger layered crowns I often build the whole cornice as a separate unit. There's not much to attach to on cabinets these days anyway.


From contributor D:
Cope if the crown is part of the architectural mouldings, assuming that it can be coped. Not all crowns are possible. If it's part of the cabinets, then miter it. Build it as much as possible on the ground, use glue and brad nail it from behind on the inside corners. Work with as large a section as you can without it becoming unwieldy. This works great if you're working around columns with many small pieces.


From the original questioner:
Thank you all for the responses. I've been doing this for quite a while and most everything I know is self taught. I don't even know anyone that does what I do full time. This forum is great and it's good to know that the way I've figured out to do things just might be the best way.


From contributor E:
A cope is a much better joint and can be quicker than mitering. You can pressure fit a coped joint. It will not open up when you nail it and it will stay tighter longer. The way to make copes faster than mitering is to use the Copemaster, a new machine that works like a key coping machine. Copes are done in 15 to 40 seconds.


From contributor F:
Do you cope your outside joints? Then why cope the inside ones? If it is good for the goose, it is good for the gander? The inside joint isn't going to shrink any more than the outside, especially if the material is halfway dry and if it isn't then why are you putting it up? Those puny little pins you might put in an outside versus and inside aren't going to keep it from moving, so miter it, glue it, and move on.


From contributor G:
The idea with a coped joint is that the first piece runs by and the coped piece butts up to it. When a coped joint shrinks all you see is a slightly bigger shadow line of the coped piece against the profile of the piece that butts against the wall whereas when an inside miter shrinks, both sides of the joint pull back equally revealing a open miter twice the size of the coped joint and the unfinished wood of the actual joint. On prefinished crown, if you have a good tight outside miter, glued and nailed and your copes positioned so they run with the line of sight, the outside miters will stay tight and inside miters will show a shadow line at worst. I trim a lot of retail stores in shopping malls with large prefinished crown where the material comes from the humid shop directly to the air conditioned mall. In these conditions inside miters will usually result in callbacks within a year whereas a proper coped joint will leave you in peace.


From contributor M:
To contributor F: Cope an outside corner? What is that?


From the original questioner:
I can understand the logic behind coping prefinished crown on a 12' ceiling in a shopping mall. But on my cabinet jobs, where the joint is 7-8' above your head I do not want to see even a shadow line. I usually glue and pin (if I can get behind it) my inside miters and touch-up my joints if need be. I can't recall ever seeing an inside miter open up that I've glued, although not that it possibly hasn't happened. If it's unfinished crown, Iíll probably cope. But prefinished cabinet crown, I'll miter.


From contributor C:
I think one thing to keep in mind on the coping issue is the method of attachment. When installing baseboard, chair rails and crowns to a room, we generally have to use the studs and there may not be good nailing near the corner so we nail in the corners and open up inside miters. On cabinetry with prefinished materials we have the option of keeping fasteners back from the corner. In many cases the crown floats on top so we're not forcing it against two surfaces. The prefinished is much less prone to movement. However there are some moldings that just don't lend themselves to coping. Something that helps me with coping is to start on my left and work clockwise. I'm righthanded. That way I repeat the same cope over and over until the last corner. I've never seen a coped joint on a serious piece of furniture though, nails either but you have straight and solid surfaces that are accurate. Room molding should be coped but when it comes to furniture and furniture like work, each craftsperson will have to set their own standards of work.


From contributor H:
I don't know about the rest of you guys, but I learned from experience that you cope a corner when it isn't a true 90. Running crown on cabinetry means you should have a true 90 (or 45 or whatever) but when was the last time anybody saw a true 90 on a framed wall - even if the framer got it right, the mud build-up will throw it off. You can inside miter on framed walls, but most of the time it leaves a gap underneath because the wall is never 90. Believe me, I would rather inside miter than cope because it's faster, but the application decides the means.


From contributor I:
I learned from a guy a long time ago to square cut the first piece into the corner with a partial 45 cut, just thru the first cove or dentil. The next piece gets 45ed on the saw, and then you cope out only the top portion, leaving the miter on the bottom. This lets you spring the mould into place. It will almost self install because it self aligns. It really goes pretty fast because you aren't coping the lower, usually more intricate portion, but still allows for a spring in fit. I can cope that piece of 4-1/2" crown in less than 20 seconds - the one on the Copemaster ad. I won't need to spend 2800.00 to do it either.


From the original questioner:
I never heard of that partial cope thing. I might give that a try sometime although still don't know if I'd use it on my cabinets.


From contributor E:
Coping part of a crown makes sense only if part of the crown is not cope-able. Then cope the part that is cope-able and miter the rest, otherwise why not cope the whole thing, especially if you can do it in less than 20 seconds!


From contributor J:
I miter everything - cabinet crown, wall crown, etc. I never got used to coping, and thought it was a waste of time. But then again, if I had started out coping, I might say that that was the way to do it. As above, when you miter, there is a lot more glue area, and most usually on cabinets, there is room to nail behind. I usually cut my first inside miter and nail it up. Then I cut the mate to it, long, try it, then readjust the cut if need be. I build and install my own cabinets, so I usually do not have many out of square situations, except for the framers and mudders from hell.


From contributor K:
Crown on cabinets I always miter. If the cabinetmaker did his job they are all true. When crowning on walls I always cope. The fastest method I found is a 4-1/2" angle grinder and 50 grit sanding disc for softwood and 36 for hardwood. With the grinder I can cope most crowns in under a minute.


From contributor L:
Most corners are inside. I can usually make a few measurements, make my copes, cut to my measure and nail it. My measured end tucks up under my cope, and I am done. It doesn't take brains, and is a whole lot easier than matching a miter at 92 or 88 degrees. I like the guy above who uses the sanding disc. I have seen a guy who does that, and he is slick, but I have yet to try it.


The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor A:
The key to knowing why you have to cope inside joints is understanding how wood shrinks in relation to the geometry of the joint. Wood shrinks and expands radially outwards from the axis of the grain (tubes), not lengthwise. This is not a problem for an outside corner, but it is for an inside corner. Notice how window molding always opens at the inside corner, but never the outside. The shrinking wood is effectively changing the angle of the cut, with the outside corner acting as the compass center point.

As far as gluing, MDF will take glue on any surface. When dealing with real wood, end grain can only be glued by first painting on some glue size (water and glue) and letting it dry. When it comes to molding, gluing end-grain is a big waste of time, and is of questionable strength. Besides, I would much rather cope a joint than deal with setting a saw to .5 degree increments.



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