Kapex Mitre or Cope

[Narchel]

Hello,
I am a novice woodworker and I am going to be putting up some chair rail and baseboard moulding.  Before I had my Kapex / angle gauge, I would cope the corners.  Is that necessary still with the Kapex or should I just mitre gauge the corner, set it up on the saw and mitre.  If I do cope, do I still use the mitre gauge or do I just "assume" a 45 degree cut? 

Thanks for the help.

 

[vwdave]

I would still cope as the joint will be tighter and looks better with seasonal movement.  You don't need the angle finder to cope because you back cut out material so the face of the joint is tight.  Have fun with the kapex  [big grin]

Dave R

 

[ajones]

Hi cope all internal corners and only mitre external corners.
good luck

 

[fatroman]

One more vote to cope, especially if your base is tall.

Getting a good, tight fit on walls that aren't square/plumb will be easier with a cope.

 

[Ken Nagrod]

When you go to cut for your inside corners, you cut a butt joint (straight cut) on one piece and cut the other piece as though it's an inside miter cut. Then you can see the profile from the side and you can cut with a handsaw, jigsaw or RAS115 to leave just the front edge profile - back cutting. Then cut the other end to length. This method should be the easiest for you.

 

[Rick Christopherson]

The topic of coped corners is a very passionate one for many woodworkers, and because of that, you often hear a limited discussion on the nature and reason for coping. The original reason why coping was developed was as a rapid method for joining boards in a corner, but it has since then taken on more of a cult personality. As woodworking technology has evolved, the "need" for coping has decreased, but the "perception" of the need for it has not waned.

One of the greatest benefits to a coped joint is the reduced need for accurately cutting the length of a moulding piece constrained at both ends--One end is coped and the other runs long.

One of the most often repeated reasons for coping a joint is to account for wood movement. However, the longitudinal nature of the material and the structure of modern building materials does not support this. There is virtually no linear expansion/contraction in the materials nor the structure to which they are attached. Testament to this is the rigidity of the drywall that covers the structure to which the moulding is attached. While minor settling cracks may occur, you will not find appreciable seasonal expansion or contraction of the drywall material nor wood products.

Moreover, any changes that affect joint-gap in a mitered corner will also impact a coped corner. Large mouldings will of course change dimensionally across their width, and this will impact the angle they make in a corner, but those same changes are in effect regardless how the corner is constructed--coped or mitered.

That statement is true regardless whether it is an inside corner or an outside corner. Why is so much attention paid to inside corners (that are inherently less visible) than it is paid to outside corners? The answer is simple: If your outside joints aren't gapped, then neither will your inside joints be.

The key to understanding this is to understand the sense of accomplishment exhibited by woodworkers once a well crafted coped joint is displayed. A well crafted coped joint takes great skill to fulfill, and that pride of accomplishment is evident in the display of the joint, and shouldn’t be dismissed. However, over the years, that pride of craftsmanship has displaced the primary purpose of the joint, as to the actual need for performing it.

With that said, for the original poster, and especially as it applies to a non-compound moulding like chair rail; no, coping your cut is not a requirement for achieving a tight corner utilizing a modern miter saw like Kapex.

When you find it difficult to accurately measure and cut the length of a piece of moulding that is captive on both ends, then yes, coping is the proper solution. Blindly coping all interior corners solely because that's how it was done for hundreds of years, is not the proper solution.

 

[Deansocial]

coping  a corner results in less of a gap if the material shrinks rick as only 1 piece moves away from the joint compared to both moving. On an external corner the joint will only get tighter when the material shrinks.

 

[Rick Christopherson]

coping  a corner results in less of a gap if the material shrinks rick as only 1 piece moves away from the joint compared to both moving.

Maybe they grow trees differently over on the other side of the pond, but does your wood shrink in length over there?  [scared]

The expansion/contraction of wood fiber down the length is negligible.

On an external corner the joint will only get tighter when the material shrinks.

That answer is often repeated, but never critically considered. If the wood shrinks (which is doesn't), does that mean it always shrinks away from the inside corners, but not the outside corners?

Think about it.

Think Critically About it.

 

[tiralie]

The topic of coped corners is a very passionate one for many woodworkers, and because of that, you often hear a limited discussion on the nature and reason for coping.

Yes and lets not get started on cutting crown flat over cutting upside down.

One of the greatest benefits to a coped joint is the reduced need for accurately cutting the length of a moulding piece constrained at both ends--One end is coped and the other runs long.

Yes agreed. It's much easier when you have longer runs (working by yourself) to get the a good fit.

One of the most often repeated reasons for coping a joint is to account for wood movement. However, the longitudinal nature of the material and the structure of modern building materials does not support this.

Completely agree. All my issues with failed joints have been on jointing one long run of crown molding to another not at the corners.

The key to understanding this is to understand the sense of accomplishment exhibited by woodworkers once a well crafted coped joint is displayed. A well crafted coped joint takes great skill to fulfill, and that pride of accomplishment is evident in the display of the joint, and shouldn’t be dismissed. However, over the years, that pride of craftsmanship has displaced the primary purpose of the joint, as to the actual need for performing it.

On a recent project a contractor had to come back and finish off some chair rail and wainscoting that another trim carpenter had started earlier. The contractor was quit pissed that he now had to cope his corners because the previous trim carpenter in his words was "showing off" by coping all the corners.
Tim

 

[Alan m]

i used never cope my skirting (baseboard) but have move over to coping as i could never get the mitered loint to stay closed over time. over here the finish in the corners and allong the edge of the drywall is a disgrace , in and out big lumps , bits missing etc. i always found that as the crapy wood in the skirting would warp it woul pull the bottom of the joint appart and leave a gap because there was nothing behind the bottom of it to stop it.
now  i cope (with a coping saw) , not 100% jet but good enough. if the coped board warps a little there is still wood on the other board so a gap doesnt form

 

[peter halle]

To answer the original poster's question, you can certainly do it either way.  Whereas you said you are a novice, my advice is to continue to practice coping.  As Alan said, it comes in especially handy for the baseboards you plan to install - not because of wood movement caused by shrinkage, but because of movement when you install.  When you but the cope against the adjoining piece - and the coped piece is cut a little long - when you nail the new piece there is a better probability that the joint will be tight.  Whereas if you just mitered that piece, the baseboard could go tighter to the wall than you anticipated, thus leaving a gap.

Chair rail - Chair rail - depending on the profile, can be time consuming and testy to cope.  Practice will help.  But in your situation you probably want to get stuff accomplished also rather than just practicing.  If the profile is a traditional chair rail you might be better off mitering there for sanity's sake.  Movement is less of an issue there than at the baseboard area in my experience.  If you are buying chair rail from a big box store and the profile is simpler, then you might want to consider coping.

Just my two cents worth.

PS - I cope when possible.  But I am old school. 

Peter

 

[junk731]

Just to add one more stick to the fire, on a lot of high end projects its not a matter of what method you want to use its what your told to do as part of the contract. Learn how to cope, as with all things in woodworking there are reasons for coping and reasons for mitering and one method doesn't work in all scenarios. The one constant is, he who pays gets what he wants.

John

 

[Ken Nagrod]

Ok, I'm going to open my mouth here.  I contacted Gary Katz this morning, hoping he would just post and I wouldn't have to stick my nose into this debate, but he hasn't so here I go...

I agree with some points that Rick C. has posted about how wood barely moves across its length and how coping is more visually appealing.

You've got to think about 2 things.  First, the wood we use today is not the same as the wood that was readily available years ago.  A one year old child could easily count the growth rings in todays wood products.  That and the fact that there isn't much development of the heartwood adds to seasonal expansion and contraction of wood products.  Second, if you look at the side view of the cut you make in the molding, whether it's crown, base, chair rail, whatever, you will see seasonal movement in that direction (face to back) which does affect a tight joint over time.  The across the grain movement doesn't just occur in the width of the molding but also in its thickness where you're still going across the grain structure.

AND  long lengths of molding will vary enough with changes in temperature and humidity.

You will see a heel or toe change in miters that when painted, especially white, shows.

I don't care how well built a structure is.  Movement occurs all the time.  Many products move together or close enough that no human visual perception occurs.  Sometimes that doesn't happen and the tell-tale signs can be as little as a gap showing or a whole structure collapsing and anything in between like cracking.  Use of todays wood framing and molding gives way to even more movement than years ago.  That's also why new methods for affixing drywall while allowing end, edge and corner floating have been developed.  Many people who's roofs are made with trusses and who's drywall was not allowed to float see issues at the top plate where cracking of the drywall occurs at the taped joint to the ceiling.  Truss and framing movement wasn't taken into account.  Especially when houses are framed and the lumber's moisture content is still high, then dries out over time.

 

[Deansocial]

coping  a corner results in less of a gap if the material shrinks rick as only 1 piece moves away from the joint compared to both moving.

Maybe they grow trees differently over on the other side of the pond, but does your wood shrink in length over there?  [scared]

The expansion/contraction of wood fiber down the length is negligible.

On an external corner the joint will only get tighter when the material shrinks.

That answer is often repeated, but never critically considered. If the wood shrinks (which is doesn't), does that mean it always shrinks away from the inside corners, but not the outside corners?

Think about it.

Think Critically About it.

i never said it shrinks along its length, thats just stupid.no it shrinks towards the wall ie away from the piece its jointed to!

 

[Gary Katz]

Narchel,
Good for you! Don't quit coping your inside corners just because you bought a great new miter saw. In the long run, you'll be MUCH HAPPIER coping than mitering inside corners. Hers why: it's faster. Period. When you cope an inside corner you don't have to measure or even care about the corner angle. A cope joint will be tight even on a corner that is 3-4* out of square (3*in 12' is around 7" out of square--something you shouldn't run into very often!)

Coping is also faster because you don't have to measure precisely. In fact, you cut the pieces a little long so the joints will tighten up even more.

But if you miter inside corners you have to cut exactly the right miter angle, which is sometimes tough to measure. A bow three feet from a corner will NOT show up in an angle finder!  And you have to cut the pieces exactly the right length. Too long and the long points will pass resulting in a misaligned miter.

The young guys on our crew refuse to cope paint grade moldings. They cut everything a little short and they carry short mdf shims that snap off clean and quick. The shim the molding out of the corner in order to tighten the joints, then they caulk ocher the shims.

With a cope joint, you don't need any of that stuff, not even the caulking.

My field experience and reading/conversations with building scientists and wood people, differs from Steve's. Wood does move with the grain. Not much, but on a long run of base, I've seen wood shrink easily 1/16".  That can mean 1/8" gap or more in a corner...if it's mitered. Remember, one of the real weaknesses of a mitered inside corner, unless it's preassembled, is that you can't put spring clamps on it and you can't nail through the joint, both of which you can do with an outside corner. And if you assemble your outside corners with glue and spring clamps, the glue joints will have 100% full strength. Glue joints that are not secured with clamps during setting will only reach about 15 to 20% strength.

As for Steve's other comment about buildings being more rigid today, I disagree with that, too. Read Bruce Hoadley's book, UNDERSTANDING WOOD, and you'll learn how frame structures today often settle more than 1/2" in a single floor because of wood movement. but that's a whole othe story and this one is already too long!

Keep coping! Craftsmanship Counts.
Gary

 

[Gary Katz]

Ken,
Sorry it took me so long to respond. I had to come in off the Santiam River and take my waders off first.
Wood does move a lot more against the grain than with the grain and that means the miter bevel angles on crown and base will change, opening a miter as the wood shrinks. And since there's no cross nails in a mitered inside corner, and no clamps pressurizing the glue joint, it will fail, when an outside corner might hold.

But remember, it's faster! Even in S. Cal. where humidity never varies enough to cause problems in mitered corners, unless the material is installed at the wrong moisture content, Latino base crews have always coped inside corners!  Why? Because it's FASTER!
Gary

 

[Ken Nagrod]

Gary,

Thanks for posting.  I hope you didn't feel like I was rushing you.  I wasn't sure whether you were home or out on the road (time differences) and figured you were still sleeping when I emailed you.  [smile]

I remember when I first learned to cope joints and thought it was too much of a PIA and time consuming compared to choppin' some miters on the miter saw.  After a while of doing it (coping), I enjoy it and my speed has increased to the point where there is a big enough difference.  I've also been told that other trades on my jobs had seen me coping molding and told the homeowner how impressive that was.  It seemed like no big deal to me, but in their eyes, that was higher craftsmanship and added value to my work in the homeowner's mind.

 

[Rick Christopherson]

A one year old child could easily count the growth rings in todays wood products.  That and the fact that there isn't much development of the heartwood adds to seasonal expansion and contraction of wood products.  Second, if you look at the side view of the cut you make in the molding, whether it's crown, base, chair rail, whatever, you will see seasonal movement in that direction (face to back) which does affect a tight joint over time.  The across the grain movement doesn't just occur in the width of the molding but also in its thickness where you're still going across the grain structure.

Wood does not shrink equally in all directions. The ratio of movement tangentially versus radially is about 2-to-1. The statement about growth rings sounds really good at first, until you realize that there is very little movement in this direction to begin with, and therefore, the spacing of the growth rings has no bearing.

If you can see a change in the thickness of the material, it's not a seasonal problem, nor is it even a matter of installing wood that is dripping wet. I used the WoodWeb calculator for southern red oak going from 12% down to 8%, and the radial change in thickness for a 3/4" board is 0.005". That's not a seasonal change; that's putting wet wood on the wall and allowing it to dry, and it is still not considered measurable as far as wood products go.

As I said earlier, there are reasons for coping, but wood movement is not one of them, especially for flat moulding with a zero spring angle (i.e. chair rail). Understanding why something is done is just as important as knowing how to do it. When we lose sight of the reasons behind a method, we also lose sight of when it becomes important for doing it. As Gary pointed out (he posted after I wrote this), it is "speed" that is the primary driving factor for coping, and to that, I do not disagree.

 

[WarnerConstCo.]

As I get older, I find it shrinks a little more each year.

Oh, you are talking about mouldings.  Well, cope them. 

I will say that once I saw Mr. Katz using the coping foot at a road show, I ordered it and 2 dozen of those clamps too.

Coping and pre-assembly, like I watched Gary do, saves me time in measuring and installing.  Noticeable time savings, I might add.

 

[Ken Nagrod]

A one year old child could easily count the growth rings in todays wood products.  That and the fact that there isn't much development of the heartwood adds to seasonal expansion and contraction of wood products.  Second, if you look at the side view of the cut you make in the molding, whether it's crown, base, chair rail, whatever, you will see seasonal movement in that direction (face to back) which does affect a tight joint over time.  The across the grain movement doesn't just occur in the width of the molding but also in its thickness where you're still going across the grain structure.

Wood does not shrink equally in all directions. The ratio of movement tangentially versus radially is about 2-to-1. The statement about growth rings sounds really good at first, until you realize that there is very little movement in this direction to begin with, and therefore, the spacing of the growth rings has no bearing.

If you can see a change in the thickness of the material, it's not a seasonal problem, nor is it even a matter of installing wood that is dripping wet. I used the WoodWeb calculator for southern red oak going from 12% down to 8%, and the radial change in thickness for a 3/4" board is 0.005". That's not a seasonal change; that's putting wet wood on the wall and allowing it to dry, and it is still not considered measurable as far as wood products go.

As I said earlier, there are reasons for coping, but wood movement is not one of them, especially for flat moulding with a zero spring angle (i.e. chair rail). Understanding why something is done is just as important as knowing how to do it. When we lose sight of the reasons behind a method, we also lose sight of when it becomes important for doing it. As Gary pointed out (he posted after I wrote this), it is "speed" that is the primary driving factor for coping, and to that, I do not disagree.

Your trying to tell me that a piece of wood with 50 growth rings isn't substantially stronger and more stable than one with 5 growth rings?  The longer a tree grows, the more heartwood it develops which is denser and more stable than the sapwood.  The stuff being grown and cut down nowadays isn't given the opportunity to develop the same stable heartwood we used to be accustomed to.

I agree wood moves at different rates in different directions, but it does move.  As for moisture content changes in wood, I've seen and been part of many houses built where the materials get dropped off the truck, soaking wet to damp and installed.  We don't have time to wait for the wood to dry.  Better builders take that into account when they can, and frame allowing for wood shrinkage, but you can't tell me there isn't a lot of dimensional change in wood from the time of installation to a few months after completion and a 4% change in moisture content is going to start to be visible in the final product not to mention the higher amounts typically seen.  If you're focusing your point on just the change in wood thickness, that amount of change you described could very well be true.  I haven't looked up those figures.  My point is less about the actual scientifically gathered data and more about what I've seen and see in the field.  Carpenters have to develop new methods for dealing with new wood to prevent unsatisfied customers, call backs as a result, a bad reputation, quality and performance of the products installed.