Carpentry and Woodworking - To cope or not to cope?

Hi,

I just purchased some MDF crown. I like MDF base because it cuts very clean, paints nice and doesn't suffer from movement as much but I'd like to get opinions on MDF crown.

First of all, can be MDF be coped?

Is there any reason to cope MDF crown? Even MDF has some movement so perhaps it's still a good idea?

Thanks

MDF can be coped and you don't even have to do it perfectly. Since it will be painted, you can use spackle to fix any boo-boos. Get the spackle smooth and the paint hides all your sins. :D

Dave,

What I was really asking is if it's worth it to cope it. A cope is a lot more effort than a miter joint although I suppose it's works better on imperfect walls.

I have put in new 5 1/2"base molding in almost every room of my house and the miters always had a 1/8" or so gap. Like you said, it doesn't really matter since you use caulk to cover it up. In high visibility areas over hardwood or tile I made some time consuming adjustments to the miter with a block plane to get the miter near perfect. With crown, doing these adjustments to the miter might be more difficult (due to compound angles and the fact that it's awkward on the ladder) so in this case I suppose a cope might be the better choice.

For me, coping is faster and always gives a good joint. The little time it takes to cope one piece is more than compensated by the time saved with the butt joint on the other.

Now, if we could figure out a way to cope outside corners.........

Thanks chfite,

I hadn't thought of that. First cope took me 15 minutes, second took about 5 mins so it isn't bad at all.

Is the joint between crown and wall/ceiling usually caulked just like base molding?

I use caulk to clean up anything that needs it.

Well I installed the crown and all of my coped ends do not come up tight against the ceiling like the butted ends probably because I did not back cut the cope steep enough. It's only a 16th of an inch or so and I'm the only one that will notice but I'll have to be more careful in the next room when I test fit the coped ends.

If one finds the proper outside angle, there should be no reason to cope an outside corner. In all my years of doing this, if my outside corner didn't come together, its because I either didn't keep it at the same angle against the fence, ended up buying wood that wasn't run at the exact same time, or i just cut one short. The only true way to get exact, perfect miters is to use molding that was run at the same time.

They use calipers to make sure it's the same size. "Usually" but nothing is 100% Perfect in this world. About 98% of the crown work I've done throughout the past 15 years I've been doing this has been on wall units, entertainment centers, home theaters, etc. I haven't done very much coping, but if I ever do more "Room Crown", I would do it for inside corners.

No matter if it's crown, base, or chair rail, I always buy extra so I can use it as test pieces. I would typically buy a cheaper material, so I don't waste my good material. I would cut pieces until I got the right angle and then I'd know what to cut my good material at. For the few extra moments it takes to cut test pieces, could be the difference between a chop job or a clean job.