strength of door panel sets

[Carl Beckett]

Im curious to the experiences here, although it must be 'good enough' or there would be a lot of posing here.

For doors in particular, Im wondering if the relatively small surface area of the stick/cope cutter sets is really adequate?

Not long ago I did some panels and these came apart. Granted they were abused. - but the joint failed. I would prefer failures to happen at other places, so it made me wonder if anyone has experienced this?

Its not in front of me, but it seems like most of these have about 3/8" face to face grain overlap that carries the load?.... is this adequate for a high stress part such as a kitchen door? And do some have more or less? (its seems inherent in the design that they can only be so deep to match)

[scott vroom]

Carl, a properly glued & clamped 5 piece door will not fail under normal use. It's not just 3/8" of face to face overlap as you describe it; the coped and rabbeted areas are glued as well. Are you just applying glue to the tongue & groove area? You need to brush glue onto every part of the profile that will be in contact with it's mate.

[Carl Beckett]

Well, it was just a question based on the fact that I did have a failure, and I see traditional cabinetry with half lap or through tenons (bridle joints) for doors. Although there is a fair bit of glue area overall, some of this surface area is end grain so perhaps not as robust?

Frued even makes an adjustable bit set to allow deeper tenons (which someone must have requested at some point or they wouldnt have bothered):

http://www.freudtools.com/t-PremierRailandStile.aspx

And found some other threads here on this same subject:

http://www.sawmillcreek.org/showthread.php?158883-Cope-and-Stick-vs-half-lap-joint

And a book review (Frame and Panel magic) is implying the same thing - these cutters arent as robust as a traditional mortise/tenon combo:

http://books.google.com/books?id=3-QUnVulS8sC&pg=PA13&lpg=PA13&dq=strenght+of+machined+cope+and+stile+joints&source=bl&ots=9peTcBCOnl&sig=fErBZIIJzcDH85unKs-p5WSRzX0&hl=en&sa=X&ei=UglzUNLxC6fr0gHM8oCQBw&ved=0CGQQ6AEwCQ#v=onepage&q=strenght%20of%20machined%20cope%20and%20stile%20 joints&f=false

And another site I found that suggested making loose tenon mortises first, and then running through the profile bits.

[David Kumm]

I replace my sets with a 5/8" tongue and put floating tenons in the ones that will receive high use. Don't know if that is necessary but makes me feel like I'm different. Dave

[Carl Beckett]

I replace my sets with a 5/8" tongue and put floating tenons in the ones that will receive high use. Don't know if that is necessary but makes me feel like I'm different. Dave

Just saw an article about this very technique - it seems pretty straightforward way to add some strength when in doubt.....

Oh, and it looks like FWW #203 runs a strength test on a number of different designs....

[Stephen Cherry]

One other option if you would want a longer tenon would be to leave the center cutter out of the cope set and replace it with a spacer. Than way you could make a longer tenon. Then you could use a hollow 1/4 hollow chisel mortiser into the slots to make a deeper shouldered mortise.

And you could even peg this from the rear for added strength.

[Jeff Duncan]

The real issue is finding a balance between building too light vs overbuilding. One could easily use loose tenon construction on cabinet doors for a really robust product. However it's significantly more costly than your normal cope and stick joint, and that needs to be accounted for if your doing this as a business. Also in normal service the benefit will never be realized. I build my doors with cope and stick and have never had a problem. In reality it is highly unlikely a well made door will fail in normal service. The failures are more likely due to abuse or manufacturing defect. For instance, small children swinging on doors would not be considered normal use! Even so my 5 year old hasn't managed to destroy any doors.....yet!

Now as far as the failure you had....first off you already know it was due to abuse, so your door was likely NOT the problem. Second the door failed at the joint....well that's logical...it's going to fail at the weakest point. I mean it's highly unlikely the stile is going to snap in half right? So you say you would prefer if it didn't fail at the joint, but in reality the door is going to fail at a place where 2 parts meet. I just don't see anywhere else for it to do so.....unless the whole door pulls off the cabinet!

So you'll have to decide what level of joinery your comfortable with and go with that. Assuming your not doing it as a business you have the freedom to build, or even overbuild your product to your own desire. As mentioned I build my doors with just cope and stick, however....I go overboard when I do faceframes and use loose tenons, as I honestly don't find pocket screws and glue sufficient:confused: It's just whatever your going to be comfortable with at the end of the day;)

good luck,
JeffD

[Mark Blum]

I was slightly concerned about the long-term strength of that joint for the kitchen cabinets I'm currently building. I did buy Freud's adjustable tenon set, but it is a bit fidgety to go with the longer tenon as it turns the milling step into a two-step process with two bit setups. Since I was using plywood for the panels I decided to forgo that and just glued them in for a nice solid door that will never fail.

[Jay Jolliffe]

All the cabinet door I have made that were cope & stick I use a floating tenon for extra strength. I don't fell comfortable just relying on the small glue surface. That's just me & I do tend to over build things. I'd rather be safe than sorry.

[J.R. Rutter]

I recently had a door that I tested to failure. With good glue-up coverage and a tight profile, cope and stick is plenty strong for the vast majority of doors. I do like to keep the back side of the groove as thick as possible to prevent the stile from splitting out if the door is overextended - like from someone walking into it when it is open.

https://lh4.googleusercontent.com/-ZxeT0OSzjB0/UHNKui96zMI/AAAAAAAACKs/18lfj7LmmJU/s576/IMAGE_BAFE960D-6603-473D-B1DC-BB4D06441148.JPG
https://lh6.googleusercontent.com/-A1pp39QHx8c/UHNKwWQFBOI/AAAAAAAACK0/NQ72FoCOLfI/s576/IMAGE_D77DC429-201A-4F67-AA40-52AB29B92248.JPG

[Clint Olver]

For doors, I just rely on the T&G with Titebond glue. Never had an issue. For something structural, like a headboard, or something like that, I reinforce with 2 dowels at each joint. It's pretty quick and easy, and I can't imagine any wood being stronger than that joint.

C

[Dave Shute]

The joint is only as strong as the species of wood you are talking about and of course the width of the styles and rails. I have done this without dowels with 2 1/2" hardwood. To dowel this type of joint accurately one would need a boring machine, doweling jigs tend to wander a bit as you drill through them and can make it difficult to get the joint to line up properly. Just my two cents. Another thing I try to do is use 13/16" or thicker stock.