Fitting Coped Crown Molding - Fine Homebuilding

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Theres a Better Way


Fitting Coped Crown Molding

comments (6) July 16th, 2009 in Blogs
grateful.ed Chuck Miller, editor at large

Video Length: 1:27


This tip comes to us from Colin Siddall of St. Paul, Alta., Canada:

Before I made this jig, I checked the fit of my coped crown molding the conventional way by climbing the ladder and holding the coped piece in place against the installed section. This method told me that it was either a good fit or that there was a gap, but it failed to tell me where to remove the material to eliminate a gap. All I knew was that there was a high spot or spots somewhere on the hidden coped surface. I then had to locate the high spots and remove them by trial and error, while chanting those special words carefully selected by carpenters to reflect their degree of frustration.

With this fixture, I am able to check my coping without climbing a ladder, and if it is not a good fit, I am able to see exactly where and how much material needs to be removed. I simply slide my coped section into the fixture until it engages the sample piece of crown, as shown in the drawing. If a gap exists between their front faces, I view the hidden coped face through the viewing window. This enables me to identify where and how much more fitting is required by the amount and position of the light shining through the gap. (High spots allow no light to show through.) I usually get all the high spots on the first go. The fit is confirmed by a quick recheck on the fixture, and it’s up the ladder for installation.

The installed sample and the guide position can be changed to suit the particular crown molding being
installed. Although I use separate left and right jigs, they can be modified easily to check both left- and right-hand coping by duplicating the window component—representing a wall and made of plywood—and attaching it to the front edge of the base together with the installation of a second guide.

Need more help on your crown molding project? Let Tucker Windover take you through the process in a Video Workshop by Fine Homebuilding.



posted in: Blogs, finish carpentry, crown-molding

Comments (6)

stevewaz stevewaz writes: after i cut the cope i use a 4 1/2 grinder with sanding disc to take off more material on the back of the molding - i test the fit of the cope on a scrap piece of the molding - 95% of the time it fits perfect - the grinder makes for fast fine tuning
Posted: 8:50 pm on March 6th

jeffe_verde jeffe_verde writes: Set your miter station up correctly before cutting, and every mitered cope will be right, without the need to test fit. The key is to place the crown upside-down in the miter saw, with the moulding *SECURELY* held at it's correct spring angle.

Do this and you'll quickly cut perfectly fitting copes every time. Fail to do this and you'll have to fiddle and fuss and custom fit every joint.

This technique is covered in an FHB article - http://www.finehomebuilding.com/how-to/departments/master-carpenter/coping-crown-molding-techniques.aspx
And Gary Katz's website, book and DVD's do an excellent job of demonstrating the technique.
Posted: 3:53 am on July 4th

haley haley writes: The reason that most people cope is because the coped joint will compensate for any of the corners being out of square. If you cope you don't have to cut the moldings on 44.5 or 45.5, you cut them all on 45 even if the corners are out of square. If you are having problems with the cope joint not fitting and you know that you've taken enough off the back side, then you probably don't have the molding bedded correctly. There are some jigs (EasyCoper) on the market that will let you use a jigsaw and give you a uniform undercut every time.
Posted: 11:25 am on October 29th

maryOO maryOO writes: I think that this is a great idea for anyone installing crown molding. Although it may take some time to create box, the payoff will be well worth the additional time it takes. It's important when you are installing crown molding to take your time. Don't rush the job.

Remember to get well acquainted with the process and installation of the crown molding. This will help you better understand how to install the molding. You may even want to watch some "how-to" videos as well.

It's important to take your time and follow the golden rule of molding, measure twice and cut onces.

Good luck!

- Mary

Posted: 2:47 pm on August 21st

fullenco fullenco writes: I believe that anyone that installs a bunch of crown would be pretty good at coping and the time you took to do this would be wasted.
Posted: 12:27 pm on August 7th

rchampag rchampag writes: I like the jig mostly because it is cool to see the backside of the cope, but dont really think it addresses the problem of fitting crown properly for inside corners, same could be said for outsides, one could make a similar jig for that as well.

This jig seems mostly to addresses bad coping techniques, such as not enough angle being held on the coping saw to take out more of the bellies of the profile. The biggest problem with using this jig for fitting to walls is that it assumes that all your corners are a perfect 90 degrees. We all know that rarely happens. For fitting into the other 90% of the corners that one would see in the field, take the extra time to make a series of 24" test pieces with good copes that ranges from a 44.5 degree cut to a 45.5 degree cut, that is a decent range for most out of square corners. use some 18 gauge finish nails set at the spring point or snap lines at spring points with super fine chalk. Hold your straight piece up, then bring in your coped pieces to see which is the best fit. move them above or below the spring line to get your best fit, but not more than 1/8" in either direction or it will show looking down the wall lengthwise.
The best fit is your angle of cut and cope. When cutting the final pieces, cut it a full 1/16 of an inch long and snap it into place to get a super tight fit.

You still have to go up and down the ladder, but hopefully at least a couple of trips less cause you only cut your final piece once. Try a small rolling scaffold instead of the ladder as well, gives more working surface and easy to roll if on subflooring still.
Posted: 6:52 am on August 3rd

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