# Why Cope Miters?



## NittanyNation (Apr 26, 2012)

ok, i know everyone (mostly) says inside corners should be coped, my question is why? what are the advantages to coping? do you guys cope mdf or just wood mouldings?


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## WarnerConstInc. (Nov 25, 2008)

quicker, less prone to opening up when seasons change, easy to deal with crappy inside corners, you can have the piece long by a fat 1/16", I could go on........


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## Evilfrog (Aug 2, 2011)

I've always done it when hanging trim because you really get a true 90 degree corner in a house.


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## ModCo Design (Oct 17, 2011)

Personally, I like to miter everything...I go through and measure everything write it on a pad and just cut everything all in one shot, and then start hanging it. I glue all my corners with a fast cap product super glue, both inside and out side corners. I have never had to go back for any warranty work on trim, and I really hope I never have to 

I like to think I'm pretty fast at too


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## Murphy's Law (Dec 15, 2011)

Evilfrog said:


> I've always done it when hanging trim because you really get a true 90 degree corner in a house.


I'm pretty sure you mean rarely, don't you? That's the reason I always cope instead of miter.


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## GeorgeC (Jul 30, 2008)

Because they give the finished corner a better look. 

George


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## BWSmith (Aug 24, 2010)

One huge reason to cope is that it dosen't require a mitre box.

Another huge point is that you can orient the joint to take full advantage of support.

Then theres always....sight lines.


But never say never.....try coping the top joint of a pediment.Or try coping any pce where the overall length is less than the cope's spacial length.IOW's.....real short pcs.Copes also are rarely used on edge trim where the line of sight is looking down at the top of joint.....yadayada.BW


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## Hammer1 (Aug 1, 2010)

Sometimes inside corners get coped, sometimes they don't. Usually, copes are used on trim work such as baseboards, crown moldings, chair rails. They don't get used on cabinet or furniture moldings. If the moldings have a complicated profile, lots of little shapes and transitions, it doesn't make sense to cope them. 

If you are installing crown moldings in a room, the first piece can be cut with square ends and put in place. The next piece typically gets a cope on one end, a square cut on the other and this continues around the room until the last piece, which will usually need a cope on both ends. The pieces of molding are cut a little long, 1/16" or less, and sprung into place. This pushes the cope tight against the preceeding piece making for a tight fit. If both ends of the molding were cut with an inside 45, when you nail them, that joint in the corner will often be pushed open. When you have moldings that are too complex to reasonably cope, you often will use an inside miter cut that is slightly less than 45 so the faces meet tightly, then you avoid nailing right in the corner, which is a good idea with many corners, anyway. It's not like you need the corner nailed on a long piece of molding that is nailed every 16" along a long wall.

It's about appearance and practicality. Cutting a long piece of molding that goes from corner to corner in a room has to be cut exactly or the corners will show any difference, long or short. You may also have issues with corners not being exactly square and the molding not sitting at the exact correct angle. Coping only one end and leaving the other end square eliminates the need and difficulty in being absolutely precise, while giving the appearance of a perfect fit. 

Cabinetry and furniture work is different. You seldom have to worry about a little difference in spring angle, out of square corners or a wavy surface that you attach the moldings to. Furniture makers are used to finer, more precise fitting and usually aren't working with long lengths, they have more control over conditions. The joints are also more readily seen and any slight roughness in the cut or fit isn't acceptable. You won't see copes used on professionally made furniture. 

I install a lot of manufactured kitchen cabinetry. Crown and light rail moldings are often added. They are usually prefinished hardwood moldings and this is another situation where coping inside corners doesn't make much sense. It's just a lot easier to miter corners and get a great appearance rather than to cope. There can be a compromise with copes at the bottom of the moldings where it might come to a tiny point. This isn't an issue with a miter but with a cope, this point is often squared off. It's often very delicate and doesn't look quite right compared to a miter where the mating is continuous all the way.


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## cabinetman (Jul 5, 2007)

There's a lot of good answers given here. Not having a miter box might help with corners that can be coped, but in reality, there's going to be outside corners. So, learning how to use a miter box, or a CMS/SCMS would be necessary.

Coped corners are supposed to appear like a mitered joint. They can be easy to do, but following the profile takes a little practice. With either mitered corners, or coped, there are times that it's possible that the moulding pieces may not be milled perfectly the same. Being able to do the match-up might require some fiddling, or some sanding. 








 







.


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## Hammer1 (Aug 1, 2010)

I'd like to watch folks cut copes without a miter box cut first, should be interesting.


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## Evilfrog (Aug 2, 2011)

Murphy's Law said:


> I'm pretty sure you mean rarely, don't you? That's the reason I always cope instead of miter.


That's exactly what I mean. Sometimes I think spell check on firefox plays against me. Because if nothing is underlined, I don't go back and read what I wrote before posting it as closely.


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## cabinetman (Jul 5, 2007)

Hammer1 said:


> I'd like to watch folks cut copes without a miter box cut first, should be interesting.





BWSmith said:


> One huge reason to cope is that it dosen't require a mitre box.










 







.


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## sausagefingers (Oct 1, 2008)

Sadly since I've started doing a lot of production home building, I've all but cut out coping. We've got it down to a pretty good system where we always cut our inside corners at a 44.5, sometimes even less, and it always looks really nice. And with crown I didn't learn by coping so I just never picked it up. I've tried with crown, but for whatever reason always fail.


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## jessrj (Mar 30, 2012)

Inside corners end up better coped. At least if you are good at it. They don't split open as easy and they take less time. You certainly can miter them but you'll end up fighting the joint a lot more.


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## jessrj (Mar 30, 2012)

Hammer1 said:


> I'd like to watch folks cut copes without a miter box cut first, should be interesting.


I agree


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## NittanyNation (Apr 26, 2012)

love the responses from everyone. so it seems like it comes down to time, look, and untrue corners.
for the thought that coped miters wont open with seasonal changes i dont get it. if the moulding shrinks there will be a gap, would seem like mitered corners that are glue and left unnailed for 6-8 inches from the corner would be better able to withstand seasonal changes better.
me and my partner always argue about which is better.


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## jessrj (Mar 30, 2012)

Nittany Nation said:


> love the responses from everyone. so it seems like it comes down to time, look, and untrue corners.
> for the thought that coped miters wont open with seasonal changes i dont get it. if the moulding shrinks there will be a gap, would seem like mitered corners that are glue and left unnailed for 6-8 inches from the corner would be better able to withstand seasonal changes better.
> me and my partner always argue about which is better.


Yeah the seasonal change is not as big a factor as simply the tightness of the joint. It's usually easier to get a cope really tight than a miter.


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## mics_54 (Oct 28, 2008)

i never cope miters....i just cope...or miter...it easier to cope because corners arent square more often than are.


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## Trav (May 30, 2011)

jessrj said:


> I agree


I also agree

Miter them then cope with a jigsaw with a coping foot all while standing at the miter saw stand.


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## BWSmith (Aug 24, 2010)

Its an extremely simple process.My dad showed me....prolly early to mid 70's.About that time he was at the tail-end of his loooong carreer.And was working as a trim contractor....in Wash DC.They were building houses so fast then that he was makin good money JUST trimming them out.

This was done with an old Stanley mitre box....and real hammers and nails.His father was a bridge engineer(amognst other things for RR)....born before the civil war.His father was a well respected builder in the same area.Only posting to give a little background.......I followed directly in their footsteps.

I will say that I've given tips and even done pics for folks on here without a single thankyou......not by all.There are some wonderful folks on here.Its just,I......and an awful lot of other folks don't like or need to be called out on skills and "tricks of the trade".

Think I already explained a "profile block" a cpl years ago.Its a simple pc of mould thats cut at a convenient length.Theres a cope on each end.Its used as a marking guide for the copes profile.It has some significant advantages in the world of mouldings.Whether anyone wants to accept the method or not.

No,its not the end-all trick.Its simply what it is.There are times....one being 40 feet up in the air doin big cornices(churches,public biildings,ect)where,if you've ever done any would know the problems passin material back N forth.Another is pure speed,another is accuracy,ect.ect.

Further,if you'd answer to yourself why the mitre cut is made in the first place,when doin a cope.......its to get the profiles outline.You'd see that this step is unecessary.It,(mitre cut) also...."CAN" be source for inaccuracy.IOWs....you have to get the mould perfectly situated to make the cut....and I mean perfect.Because if its not,you've effectively blown your accuracy quotient out of the water.Theres some cosine error in there that gets beyond most folks pay-scale......and to a degree past mine.BUT I do understand the error....and heres the kicker,plan for it.


Its that last sentance that needs to be taken and stored in the computer bank.A profile block is a very simple affair.The reason its more accurate is because of cosine error.These errors show up....or maybe better stated,can show up in pretty much every aspect of layout.Realizing their existance(potential error)is only a step in the process of wood mastery.Best of luck.BW


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