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Having Trouble Coping
I am trying to install crown molding. The
molding is about 5 inches wide. I find that the room of course is not
square. I know I am to butt and cope the inside corners but they are not
fitting in. Please tell me what I am doing wrong.
Thank you,
C.R.
If
everything seems to be lining up, but there is still a small gap that
won't close, then I think I might know what the problem is.
When making the coped cut, most carpenters will angle the saw so they
are cutting away extra material in behind. In machine shop practice this
is called a "relief angle", and it means that some excess
material behind the scenes is removed.
The result is what I call "a knife edge", that is, the coped
end is not blunt but sort of pointy. If taken to an extreme, you could
fashion a spear this way, and the visible surface of the crown molding
would look just fine, because where the saw meets the face, the cutting
occurs along that perfect line (the line you made by first cutting a 45
degree miter in the wrong direction).
So imagine your coped crown molding, held against the ceiling but not
quite in position yet. You slide the board towards the other,
full-length piece. The first wood to contact the full piece is... the
knife edge... because the wood that's behind it has been cut away. The
result is a little void behind every coped corner. You'll never see this
void, but it's behind every properly coped baseboard and crown molding
on the planet.
When you use this "knife edge" approach to corner joints, you
can get them very tight and they stay that way
Try it on some scraps, if you can make sense of my description, and see
what I mean. This is one of those neat little secrets of carpentry.
Bruce W. Maki, Editor.
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