cabinetman

IMO, there's no geometry to it. It's just a matter of following a line that's the shape of the moulding.

Streamwinner

There's a lot of geometry to it. Following the profile line doesn't work when the moulding goes up, down, then up again (see pic).

Willie T

It's simple backcutting. Don't contribute to the mysterious shroud of voo-doo. You lean the saw, and cut. True, sometimes you change the direction of the lean some, but this becomes second-nature after a bit of trial and error fitting.

Streamwinner

Voodoo? Really?

Actually, "simple backcutting" doesn't solve the problem with this particular molding. If you consider how an adjoining piece comes in at 90* to the face, the problem is that there will inevitably be a space on the other side of the lip at the top.

mwhafner

Streamwinner,

Can you post a picture of an attempted coping of this molding? It might help demonstrate the issue to other members.

Willie T

Can you imagine that you could actually get about four inches of the piece you are coping shaved down to only the width of the paint/finish on the front? Now, would not that coped edge fit snuggly against the previously intstalled piece? Of course it would.

This is what you esentially accomplish by backsawing at what ever angle is necessary at the various points you are reducing. No, it will not all be a one-direction backcut. You may end up cutting one area back toward the far end of the piece, while backcutting another area toward the top or bottom, etc.

Streamwinner

Thanks. I don't have a photo because this was awhile ago. But hopefully this pic will help others understand.

Attached Thumbnails

 

mwhafner

Great visualization

If you look at the blue arrow on Streamwinner's last post, you should be able to see why this molding cannot be coped.

plyboy

I would simply take the angle of the walls with my Starrett angle finder, and cut an accurate mitre joint. If possible, then I would glue and nail the joint from the back then get help to raise it and nail it.

You would have to cut the mitre joint first anyway so as to establish a cope line. Common sense would then tell me that unless I want to knock down the wall, install the coped crown from the rear, then re-build the wall, I would opt for the mitre joint, which would be quicker.

Nothing wrong with mitre joints, especially if they are glued and nailed from the back. Much stronger joint than a coped joint.

A coped joint is not a structural joint, it's just for looks. And to hide expansion and contraction, but a glued and nailed inside mitre will get you the check on Friday just as well, especially if it is a perfect fit.

Some things are just plain contrary to common beliefs. Don't fight it.

If the river can not go over the rock, it will go around it, but it must keep flowing. You are the river, That f**ked up crown is the rock. It's only a job. Get it done. Quick as possible. Don't have a cow.

The mitred joint is still a highly respected and noble piece of joinery, if done correctly. (Anal retentives may biscuit the M.F.).

Now GET BACK TO WORK!

plyboy

I would simply take the angle of the walls with my Starrett angle finder, and cut an accurate mitre joint. If possible, then I would glue and nail the joint from the back then get help to raise it and nail it.

You would have to cut the mitre joint first anyway so as to establish a cope line. Common sense would then tell me that unless I want to knock down the wall, install the coped crown from the rear, then re-build the wall, I would opt for the mitre joint, which would be quicker.

Nothing wrong with mitre joints, especially if they are glued and nailed from the back. Much stronger joint than a coped joint.

A coped joint is not a structural joint, it's just for looks. And to hide expansion and contraction, but a glued and nailed inside mitre will get you the check on Friday just as well, especially if it is a perfect fit.

Some things are just plain contrary to common beliefs. Don't fight it.

If the river can not go over the rock, it will go around it, but it must keep flowing. You are the river, That f**ked up crown is the rock. It's only a job. Get it done. Quick as possible. Don't have a cow.

The mitred joint is still a highly respected and noble piece of joinery, if done correctly. (Anal retentives may biscuit the M.F.).

Now GET BACK TO WORK!

Streamwinner

I agree. I ended up mitering all corners, but I didn't think of nailing it from the back before putting it up; I just glued them.

I initially wanted to cope them because they are solid oak, and I was worried about expansion and contraction. That's when I wasted practically an entire day.

Gus Dering

Lets say you have a room 12' x12', nice little square room.

Are you saying you would do this room with a scarf joint on each wall so you can back nail each corner?

If that was the case I would not be pleased with the results. IMO that room should have no scarf joints at all.

That crazy profile is not cope friendly for sure but back nailing would take a back seat to full length runs.

Willie T

Had some insurance damage work done at our house awhile back. The trim guy showed up with 8' sticks of base. "Because it fit in his van." I sent him packing.

plyboy

The backnailing is only done wherever possible. Like runs longer than 12 or 16 ft, (do both corners first, then fill in the middle). Or for short runs that go to an outside corner, like offsets. If any joint needs to be completed aloft, I prefer it to be an outside corner rather than an inside one. On one piece runs with a moulding that can not be coped, simply cut it a smidge longer and spring it in. It will look great forever.

All offsets, and short jogs should be pre-assembled completely before going up, both inside and outside corners.

If I am mitering, wherever possible, I will backnail all my inside joints. It avoids having to shim behind an inside mitre to make it right. Difficult to do with short wall to wall runs, but not impossible if there is a door or window to poke it through for a minute. This method is only for production crews of 2 because you need help raising the backnailed moulding if it extends out in two or even three directions. It looks kind of silly when three guys are lifting three pieces of crown moulding, but it only takes a few seconds and it turns into quite a dance production when doing "production" finish carpentry.

I think that coping was invented by a guy who was stuck working alone.


I was a carp sub at a hotel-condo conversion a few years back, and ran crown in 500 one and 2 bedroom units with one other carpenter and only one chopsaw. One floor of 25 units per week including hallway. It was quite a dance. But that's another post altogether.

I apologize for drifting this thread off it's original course. Let's get back to coping.

I recently did a series of double-end crown copes in a house where a customer decided after the wall cabs were hung and crowned, that he wanted continuous crown rather than it dying to the wall wherever the wall cabinets ended. Needless to say, he was impressed that I didn't disturb the existing crown and a little more educated as far as woodwork goes. "Coped joint " was a major part of his vocabulary for a few days following.

Texas Sawduster

I just finished putting up crown in my den re-model.
The room is approx. 19 x 19. I had not thought to back nail the corners and work the middle last.
That would have saved me alot of frustration trying to get the saw cut miters to mate.
Of course I was doing this by mself so I have only one corner that turned out decent. Thank God for putty and paint.

mencheman

I have Dykes # 185 Crown molding with an actual 3 1/4 projection and from ceiling to bottom 3 3/8
According to the molding book it should be 3 1/4 x 3 x 31/4

how ever when I turn it upside down and backwards to cut a 45 and expose the profile for the left side of an inside corner I cannot get a good cope. it is open by 1/8 on the top.
When it sits on the miter saw up and backwards , it measures 3 1/8 x 3 3/8.
i took it to a friend who is a cabinet maker and he cut it as it would lie against the wall and ceiling only with the profile towards the fence of the saw- a very difficult way to hold the piece.

I cannot get to the bottom of this .
Can anyone help. I watched the videos and i know I can follow the profile of the crown very well and i have a severe back cut
It seems to me the angle is keeping it open at the top