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.
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:
Slice the molding @ 45 degrees in the miter saw (like an inside miter
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
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
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
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.
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.
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
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.
"You can lead them to LINUX
but you can't make them THINK"
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
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