coping sanity check


Hello,
I have a cope joint to make in some 2.5 inch mape crown moulding. I just need a quick sanity to check to make sure I'm doing this right because my first couple of test pieces just weren't making it.
First I put an inside miter on the crown. I do this by laying the crown upside down against the table and fence of my miter saw and mitering it at 45 deg. This worked fine for the outside corners so I'm assuming it should work to get an accurately cut inside miter. If it doesn't then I must be really missing something....
Then I mark the curved end with a pencil.
Then, as one previous poster suggested, I back cut it wayyyyy past where I think it needs to be back cut to, and then back cut it a little more following the pencil line on the face of the cut.
When I put the coped end up against a butt end at the spring angles they don't even seem to want to meet. They are kinda sorta getting there but they aren't close enough to where you could start cleaning them up with a rasp.
Am I missing something fundamental here?
My cut along the face was pretty accurate, not perfect, this stuff is really hard to cut, but pretty close to the line. Maybe not back cutting enough?
thanks ml
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snipped-for-privacy@yahoo.com wrote:

All the miter does is show you the contour of the molding. You then cut (at 90 degrees) along the contour. When finished, the end is sort of a reverse image and fits by butting the end against the side of the other piece. You can fudge the 90 degree cut slightly, beveling toward the back except at bottom, so that only the leading edge of the coped piece contacts the other.
If that's what you have been doing, I haven't a clue as to what you are doing wrong.
-- dadiOH ____________________________
dadiOH's dandies v3.06... ...a help file of info about MP3s, recording from LP/cassette and tips & tricks on this and that. Get it at http://mysite.verizon.net/xico
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yeah, that's what I've been doing. I don't have a clue what's going wrong either. Gonna go pickup some mdf crown at the despot today and practice some more on that. If I can't get that stuff coped right I'll never be able to do this maple.
thanks ml
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snipped-for-privacy@yahoo.com wrote:

For crown molding, doesn't the bevel need to be a compound bevel?
E.g if you were using a chop saw you'd clamp on a sub fence to hold the molding at a 45 degree angle with respect to the table, e.g. leaning against the fence, and then angle the saw at 45 degrees to chop straight down. With a compound chop saw you can probably do that face-down on the table, a cow-orker did his that way but first he did all the trig to figure out the angles. Not sure how to do it with a table saw.
Maybe you should try an analog approach. Hold the mating piece against it, with both at the angles at which they will be installed. Of course you won't be able to hold them tight together, they will only touch at one point. Then hold the side of a pencil flat against the face of the mating piece so it overhangs the end far enough to reach the face of the other and roll the pencil down to trace the contour on the other.
Then cut that out with a coping saw.
If either method works, let me know };-)
Also, walls are notoriously unflat and unperpendicular at the corners where the plasterers may have used a little more spackling than else where in the room.
--

FF


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On 19-Jun-2005, snipped-for-privacy@spamcop.net wrote:

that's the reason it's held at the spring angle while cutting.
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snipped-for-privacy@yahoo.com wrote:

Ok, maybe it is nonflatness of the underlying plaster work that is causing problems. Can you use a carpenter's square to see how true the corner is?
--

FF


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ML:
This will be very hard to explain with just words, a picture is worth a thousand of my words. And please, someone who has an idea of what I am saying, please let me know if I am being clear or just confusing the OP with bogus words.
Cut a 6 inch test piece of CM and both ends are chopped at exactly 90 degrees to face of CM. This is your square miter test piece.
Now, as you have been doing, make a 45 degree compound miter cut on another test piece, say 8 inches long. We will call this your miter test piece. This would be as if you were going to make the inside corner a miter cut, (if I can explain it) the miter goes from the face of the molding out to the back of the molding, and the back has a longer length than the face.
Let us call the miter cut from the face to the back of the CM the 'miter waste'. Take a pencil, or some sort of marker, and lightly darken the miter waste, and only the miter waste. The point(s) where the miter waste meets the face, make a real dark curved line. Take your time and be accurate.
Now on a flat surface, using some scrap wood as help, lay the mitered piece on the table at approximate angle it will be installed at (the top higher than the bottom of the CM.)
Now hold the square piece perpendicular to the miter piece, but at the approximate angle it will be installed. (Normally this would have the part of the CM furthest away from your body angled to your left and the closest part, or bottom of the CM, angled to your right.) Now move the entire square piece to the right along the miter piece until the square piece reaches the edge of the face and miter waste. Keep the installation angle as best as you can.
The contour of the square edge piece should match the darkened line on the mitered piece.
If it doesn't, you have a problem with your compound miter cutting. Post back and I will try again to explain the process using standard Quarter round molding..
If you see that it matches the darkened line on the mitered piece, then you now know what has to be removed. You want to remove the entire miter waste along that darkened line on the miter test piece. Aside: you will find the match up works best with both pieces at the correct installation angle.
Gosh I hope this helps.
Phil
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On Sun, 19 Jun 2005 17:41:02 -0400, "Another Phil" <NoSpamming@one two three four five.com> wrote:

<<snip>>

Here are some pictures, the description you gave should be enough to fill in the gaps.
http://www.taunton.com/finehomebuilding/pages/h00004.asp
There is a link on the last picture on this page that shows the coping process in greater detail.
Also, for the OP- make sure that 45 degrees is the angle you need. I've run across crown that sat at a slightly different angle, it was several years ago, so I don't recall if it was by design or because the corner was off square, but I've cut them at as little as 30 degrees to get them to fit properly. (on reflection, the crown extended further down the wall than it did onto the ceiling, IIRC, so the angle was less extreme.)
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MDF is NOT a good trial base for coping. The fuzz and other bumps left while "adjusting" the fit will be even more difficult. Buy the cheap(er) finger jointed pine for learning. Coping is a pain in the ass, but coping mdf is even worse.
IF you have a Dremel tool...get it out. A Dremel tool with various cutters is a wonderful "coping tool"...
snipped-for-privacy@yahoo.com wrote:

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Remember as you cope that the 2 pieces of crown are meeting at a steep angle, not in the flat like baseboard. I suspect you are not keeping this thought in mind as you cope the piece. To get the feeling, hold a piece at about the install angle as you cope. This will be very awkward, but it may give you the idea.
(top posted for your convenience) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Keep the whole world singing . . . . DanG (remove the sevens) snipped-for-privacy@7cox.net

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On Sun, 19 Jun 2005 16:00:39 GMT, snipped-for-privacy@yahoo.com wrote:

This is correct as long as you are holding the crown at the same angle as it fits on the wall. I assume that you did this on the outside cuts so I think you have that correct. You might check it by taking one of the pieces with an outside cut (that you know is good) and hold that on your fence as if you were going to cut it again. Without cutting, mark a pencil line on your fence along the top (which is really the bottom) of the crown. When you get ready to cut your inside 45s bring the crown up to your reference mark.

You are on the right track. Make sure that the piece you are fitting to is installed at the proper spring angle against the wall. If the cope is more open at the top or bottom (not all the way along it's length) this is usually evidence that the first piece is installed too high or too low. You can cut and cope the proper angle on the new piece but if the installed piece is too high (on the wall) or too low a good cope will not fit. You can measure the reference mark on your saw fence and measure down the wall to be sure that measurement is the same.

You can try to check that by rubbing a pencil all over the high spots on the back of the cope. Then, hold it up to the piece on the wall and kinda wiggle it a little to see if you can transfer a mark to the piece on the wall. If you see some marks on the installed piece you will know that the back cut is not enough and also where you need to take some out. I know this isn't too scientific but assuming that all of the other things mentioned above are correct, this is worth a try. I've been coping crown for a long time and once in a while I still won't get enough undercut.
Good luck and let us know how it's going.
Mike O.
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Ok, headed down to DixieLine and got some samples of mdf and fj crown narrow and wide. Been playing with the narrow so far. Just did one on the narrow fj that I could put up and not be totally ashamed of. Wasn't able to do that with the narrow mdf. A coping saw doesn't seem to be the best shaping tool to use for the mdf aside from removing bulk waste and even then there's probably something better. For the fine shaping I bet a dremel with a tiny rasp would work great.
The saw worked fairly well for the fj and that was fairly straightforward. I could probably use a blade with more tpi. Am using 20 now. I see that Rockler sells 32 tpi narrow blades which I'm almost certainly going to have to use for the maple.
The mdf I played with didn't spring really cleanly either, i.e. it's wall mating side and ceiling mating side weren't really square. That probably was a factor in the problems I was having with it. I'll try compound cutting that sitting flat and see if it has any effect.
I expect the wide crown will be easier finesse wise.
Too bad I can't rent one of those new copemaster things. :P
ml
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On Sun, 19 Jun 2005 23:57:11 GMT, snipped-for-privacy@yahoo.com wrote:

Hold the crown inside a framing square and see where it hits on the top and bottom. You will know when it's where it needs to be. Most crowns will not fit the corner an equally distance away from the wall and down from the ceiling. Most we see measure farther down the wall.
As far as the under cut goes, with the piece laying flat, your coping saw will need to lean more than 45 degrees. I'd guess closer to 60 but I haven't ever really checked that.

I've kinda lusted after one of those myself but at about $2500 I can cut a lot of copes by hand.
Mike O.
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wasn't a matter of the spring angle not being 45 deg. It was a matter of the outside profile of the overall moulding not being 90 degrees. So it didn't snug well at the spring angle between the table and the fence. Just did a wide mdf one and it looked pretty good. I'm getting there.
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this very subject. A picture is worth a thousand words (give or take a few). Tom
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I've got it down now. It was mainly the fact that I wasn't back cutting enough and waste material was keeping the pieces from mating correctly. It's also that the fact that this is an order of magnitude or so more delicate shaping of wood than I've done before.
Also having a clue on how to really use a coping saw helps. This I developed over the past couple of days by trial and error.... mostly error. Not to mention a sharp blade makes all the difference in the world.
we shall see how well my pine acquired skills translate to this maple. ml
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On Tue, 21 Jun 2005 02:08:00 GMT, snipped-for-privacy@yahoo.com wrote:

This has always been the biggest problem for anyone who I have tried to teach coping with crown molding. It just doesn't seem that you should have to get that much undercut. Once you do, the pieces fit right together. Good job.
Mike O.
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snipped-for-privacy@yahoo.com wrote:

Who copes anymore? I havent coped a crown molding in ages. I strickly miter the inside right and left. It much faster and comes out much cleaner for me anyways.
Rich
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On Tue, 21 Jun 2005 02:16:00 GMT, EvoDawg

That would be me.
Mike O.
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snipped-for-privacy@yahoo.com wrote:

Here's a simple fix to your problem. I do crown molding for a living and I'm giving away a little secret here, but most of what I do arent do it your selfers.
http://www.cutncrown.com/index.htm
You will never cut crown without it again!!!!!!!!!!!
good luck Rich
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