miter crown "into" existing crown

  • Advertise with us

« back to Wood & Lumber forum

Forum topic by lothian posted 03-16-2012 11:01 PM 5235 views 0 times favorited 13 replies Add to Favorites Watch
View lothian's profile


4 posts in 3341 days

03-16-2012 11:01 PM

Topic tags/keywords: coping miter crown molding

I’ve searched around these forums against the topic “mating existing crown to old”. The discussions tend to cover the dilemma of mating old and new profiles. My situation seems unique: specifically, I need to miter new crown into existing to make a 90 degree inside corner.

I removed a 12” section of existing crown in order to continue a box column to the ceiling. I need to wrap the crown around the column, but I can’t seem to miter a piece to mate perpendicularly into the existing. I cut the new crown at a 45, then coped it to fit into the existing crown, but it doesn’t fit. I’m stumped. Any suggestions? Here’s an illustration of my problem…

13 replies so far

View devann's profile


2260 posts in 3771 days

#1 posted 03-17-2012 12:51 AM

Try a coping saw. Cut your crown as though you were going to join two miter cuts at right angles. Then follow the cut with your coping saw. A bastard file may come in handy for a little touch up.

-- Darrell, making more sawdust than I know what to do with

View Grandpa's profile


3264 posts in 3754 days

#2 posted 03-17-2012 01:52 AM

devann is correct. Cut the 45 degree cut then cope the line where the cut begins. If the box is not 45 degrees then the saw might need to be adjusted to something other than 45 deg. I like to use a protractor on a machinists square. I can read exactly what the angle is then I can adjust accordingly (half of the angle you read). I try to cut the back shorter than the front of the cut. use a half round course file and shape it a bit if necessary. Once you establish that cut then you can mark and cut the outside corner to length. I also use the protractor to read this angle so I can make it perfect. If the molding is not exactly the same as the original it will not fit. I have seen pieces bought out of different lots that just didn’t work together. Sometimes it can be different mills or the blades have been ground or whatever. It has to be exactly the same molding.

View Loren's profile


11190 posts in 4726 days

#3 posted 03-17-2012 02:01 AM

45 degrees may be the wrong angle. Crown comes at
different “spring angles” and 45 is not the most common
from what I’ve seen. In order to cope the new crown
into the old, you need to know the spring angle of
the old crown…. well, there are other ways, but I suspect
you may not be grasping some key principle of crown
installation and geometry.

Mitering your new crown at the outside corners will challenge
you as well… if you get the spring angle wrong.

I make scrap boards with the same back-side bevels
if crown is not making sense to my brain… then I play
with the scraps until I think I’ve got it figured.

View Grandpa's profile


3264 posts in 3754 days

#4 posted 03-17-2012 02:04 AM

This is true. If the molding is not on the corner at a 45 degree angle then things change again.

View ben10's profile


42 posts in 3467 days

#5 posted 03-17-2012 01:19 PM

Did you cut your mitre (on the chop saw) with the molding upside down on the table? Then use your coping saw.

-- Ben

View DustyRich's profile


12 posts in 3397 days

#6 posted 03-17-2012 01:50 PM

The typical crown molding seen in houses today is a 38-52 degree crown. It does not sit at a 45 degree angle to the wall and ceiling, it sits 38 degrees from the wall to the ceiling and 52 degrees from the ceiling to the wall. My late father in law and I installed hundreds of feet of crown in old houses with uneven ceilings and out of square walls and coping the corners made it look square. If you a small piece of the crown, 4”-6”, place it upside down on your mitre saw and check when the ceiling portion (flat on the table) and the wall portion (on the fence) are both flat against there respective surfaces. When they are, mark a line on the fence and and the table with the mitre set a 45 degrees both ways and when it is square. This way you will have a references that will keep the molding at the right (correct) angle. If it is primed or stained, when you cut the mitre, you then take your coping saw and cut down the profile between the the surface and the meat of the molding. Angle the saw back into the molding so you cut out enough that it does not interfere when you place it in the corner. A 4in 1 rasp or file helps clean up any leftover that may be in the way. Once you get the first good joint, the rest will be easier. I does have a bit of a learning curve so be patient and good luck.

View lothian's profile


4 posts in 3341 days

#7 posted 03-17-2012 06:31 PM

b’wooof… I presumed a simple three-sided wrap of crown would take five minutes with a compound miter saw and an air nailer. However, my experience coupled with my inexperience and my naiveté guaranteed it’d morph into a multi-tooled project with too much scrap.

The consensus to my post is that the angle of the existing crown was the source of the problem. It was.
So I got the mounted angle of the existing crown, then let the computer determine the profile for me… virtually. (...If only a CADD-CAM driven tool existed to make the actual cut, eh?) The required profile cut of the new crown appears in the illustration below. I set my saw to match the mounted angle of the existing crown, then used my Dremel to form out the profile shown in the illustration. To my amazement, the pieces fit.

Thanks a whole bunch for the help!

View Brian Wohn's profile

Brian Wohn

97 posts in 5142 days

#8 posted 01-31-2021 12:45 PM

Just came across this old post, but SOLVED my BIGGEST PROBLEM! I do a lot of built-ins for clients and they want to tie-in there existing crown molding with the upper shelves/cabinets.

I’ve been trying to find a way NOT to have to make those ugly corner blocks when tying in peoples existing crown moldings. They always want it “built-in” look with existing crown. I used to tell them they have to take it all down and reinstall, but I was trying to think of a way to make a jig that I can put on the wall and cut with my multi-tool – getting the angles/compounds right, etc.

Then, DUH, I saw the old “coping” crown – that no one does anymore. I’m going to test it out, but should work great. I just square cut where my uppers go in, then COPE the new front one. Probably don’t even have to cut it, since I’m just moving it forward… WHAT! haha

See video demo of a Rockler coping jig – to make it easier of course:

-- Brian, Pelham, AL

View Robert's profile


4553 posts in 2559 days

#9 posted 01-31-2021 01:17 PM

Forget the compound angles they don’t work for coping anyway.

Position it upside down and against the fence and table like it would be in the wall & cut at 45°

-- Everything is a prototype thats why its one of a kind!!

View Brian Wohn's profile

Brian Wohn

97 posts in 5142 days

#10 posted 01-31-2021 01:36 PM

I know not to do a compound miter angle, my point was the coping the molding to fit the existing :)

-- Brian, Pelham, AL

View 1thumb's profile (online now)


375 posts in 3235 days

#11 posted 01-31-2021 03:46 PM

edit: Didn’t see you had solved problem. I got to go grocery shopping

-- I actually have two thumbs and they oppose.

View Axis39's profile


482 posts in 675 days

#12 posted 01-31-2021 05:35 PM

When coping crown, you have to REALLY undercut it… The angle you would use on say baseboard is not steep enough. The end of the coped crown ends up looking too angled, too skinny, before it’s right.

-- John F. SoCal transplant, chewer uppper of good wood

View Brian Wohn's profile

Brian Wohn

97 posts in 5142 days

#13 posted 01-31-2021 07:28 PM

I see – thanks for the input guys!

-- Brian, Pelham, AL

Have your say...

You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics