Rotozip for coping crown molding

[eganders]

Has anyone out there uses a rotozip for coping the inside miter of crown molding? What did you think?

[Amused]

I think I tried it once. I think I can't hold the rotozip nearly steady enough to be useful. I do think that if someone created a ultra-small "router table" that would hold the rotozip steady (tilted at an angle) and then you could feed the mitered joint into the bit, using both hands and the table top for stability...you might have something there.

I'm quite certain that I saw Tommy Silva (This Old House) use a specific power tool to automatically cope the joints. And I'm relatively certain he said it cost about $1500.

James...

[B a r r y]

One could also either install a "coping" foot on a jigsaw, or build one of those triangular coping boxes. The box just might work with a Rotozip. Personally, I do them by hand and finish up with a Dremel with a carbide rasp. After 2 or 3, they go quickly.

Collins Coping foot:

By hand:

Slice the molding @ 45 degrees in the miter saw (like an inside miter corner) Darken the cut line with a pencil Cut the cope near the line with a coping saw Grind to the line with the Dremel, including the back bevel

Barry

[Tom H]

[B a r r y]

read a mini-review, if you get the chance to post it.

Barry

[Evo]

I think coping miters is a waste of time. I miter all my corners and they come out looking perfect. Cut them flat on my 12" miter saw with the correct miter angle and bevel and you don't see a joint. Measure on inside

90's from the bottom long angle cut 1/16 over, spring into position and your done.

RV

Oh and btw I do this for a living, exclusively. Mostly 6-8" crown and multi-layered too. Cathedral ceiling, bay windows whatever. $5.00 to 8.00 a foot is a nice round number depending on what it is. So glad crown has come back into style. Busy always and making a killing!!! Thanks Tom Silva and TOH!

[eganders]

What about if the ceiling is not a perfect 90 degrees? How do you compensate for the miter angle. Do you measure the inside angle and compensate?

[Dave Jackson]

I've never thought of using a Roto-zip for coping, however, I've tried a few different methods, including the Collins coping foot (Dave Collins lives in the next town over)and just mitering. My prefered method still involves a regular coping saw and a 4-in-1 file to finish. --dave

[Evo]

I use a long protractor that determines the angle. If it's a 88 degree you set the miter to 44 degrees. There are tables in good crown molding books that give you the bevel angle according to the spring angle of the particular crown your using, usually 38* 45* or 52* You cut it flat on your miter, no need to do the upside down and think backwards routine, and angle it on your fence and have a stop to hold it. This is great since most miters have a hard time with 6" or wider crown against the fence.

It also helps to have a couple of templates of the cuts specially inside ones that you label inside left, inside right so you can use them to setup the right side of the crown to cut. When you install as much crown as I do you don't need to do this.

[ATP*]

use a regular coping saw- takes very little time.

[B a r r y]

Have you seen them a few years later, or just right after you're done? Do you usually install painted MDF or stain-grade, solid wood stock?

I can't believe how many homes and businesses I see with mitered inside corners on crown moldings (base and chair, too) that are wide open in the winter. Sometimes, you can even see where the installer tried to glue the corner, and the broken dried glue is visible in the joint.

Barry

[George]

Probably why those that don't cope use flexible caulk under the paint, no?

[Evo]

So what your saying is coped cuts don't expand and contract with the change of weather? I do both, mostly these days MDF painted white, that is the style for now at this time. The only time I use a coped cut on crown is in a bathroom with solid wood. The humidity changes are extreme. I live in Southern California and the humidity changes are slight even while it's raining. I said in my opening that I cut over and spring the crown in place.

I don't use caulk or glue except when I do a splice on long pieces, no need too. Sorry to disappoint you when it comes to copes but I just don't see them as necessary anymore at least where I live. I have seen my miters years later when folks have called me back to do other rooms and they look as good as the day I put them up.

[B a r r y]

Of course not. Coped joints hide the movement better.

I live in New England, where we get some summer humidity and dry, cold winters.

I didn't see any location reference in the original post. Your corners wouldn't look so good later in many other places.

Barry