box joint testing

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Assuming, of course, that "proper" includes using a suitable glue. Hot melt and cyanoacrylate being examples of unsuitable glues. Possibly also hide glue, depending on the type of joint.

"Strong enough" is probably true in most cases. I think a tenon which fits the mortise in both directions is stronger (and if I remember correctly FWW's test a few years back confirmed that), but it's probably stronger than it needs to be for most applications.
Something which takes a lot of racking force across a small joint, like a chair assembly, would probably benefit from a fully-formed tenon.
John
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On 12/21/2015 2:01 PM, John McCoy wrote: ...

I recall the article pretty well; I don't think this particular point was in the test matrix.
What was, best of my recollection was the loose tenon and standard and some minimal amount of testing for a "loose" vis a vis "snug" tenon in the mortise to illustrate a "good" and "not so good" quality of fitting the tenon but I do not recall the squared tenon in the rounded/routed mortise.
It's obvious from simple mechanics similarly to the obvious conclusion above re: a pocket screw that the should requires crushing the material to move whereas the open area requires "only" moving the glue with at least initial deformation of much less material for a given amount of racking displacement.
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Are we thinking of the same article? FWW has done two or three tests of that nature - according to the handy-dandy index, the one I'm thinking of was in issue 203 (and, of course, when I look at my stack of magazines, it goes 202 - 204, and 203 is nowhere to be found).
Anyway, I do recall M&T joints were found to fail by the tenon breaking, and while I don't recall if they postulated a mechanism for that failure, I'd worry that a short tenon would be more prone to break.
John
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On 12/22/2015 1:42 PM, John McCoy wrote:

Well, that turns out to be the same exercise here; found all around that but didn't find the particular issue.
All I'm saying is that to best of my recollection there wasn't a test of the difference between the fully-filled and the rounded mortise/squared tenon in that comparison. My follow-on opinion based on just the mechanical properties of the joint geometry is that the unfilled joint will be somewhat weaker in comparison to one of the same size tenon in racking since there's not the full shoulder to bear upon if that test were to be done.
As for the failure mode specific in the test done, I don't recall; I think cannot, however, draw too broad of conclusions regarding the failure mechanism for a joint class generally from the specific tests run therein; those results are specific to the specific joints and the specific geometry used. They're representative of those in that general size but the results could well be different, particularly on the "how" of the failure as the proportions and dimensions are modified away from those in the test sample.
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On 12/22/2015 3:17 PM, dpb wrote:

I always think there is the book guys doing tests, and real life. Sometimes (often) the so called book guys get lost in the numbers, and the fact they want to say something important. Often they are correct but meaningless in the scheme of things, and too often, they just lie.
Anyway, I've been doing cabinet work for a whole lot of years, and never once had a mortise and tenon joint fail, and believe me, not all of mine have been perfect by any stretch. About 5 years ago I made a "prototype" spectators chair out of about $3 worth of cheap construction cut offs I got at Home Depot. I designed it and redesigned it several times to get the size I wanted (had to fit at least my 280 lb body.) When I finished, it was exactly what I wanted, but was too big to fit in my Billiard room. I didn't want to throw it away, but because it was not made of hard wood, and the (internal) joinery was less than stellar, I thought a bit before giving to our local Moose, where pool is played on a regular basis, 3 nights a week traveling leagues, and patrons are often both large and tipsy. Quality chairs tend to not last long in these places.
This thing has been in continuous use there since 2010 with no signs of failing. Used either Borden's yellow cabinet glue or Titebond III, don't recall. I know chairs put the big test on joinery, more than anything, and in a bar, the supreme test. Here's the chair:
http://jbstein.com/Flick/PoolChair1030948.jpg
http://jbstein.com/Flick/PoolChair1030955.jpg
If this thing held up, I wouldn't worry much about Domino's or square tenons in an oval hole. Glue is pretty amazing stuff.
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Jack
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Love the notches for a cue stick, now it has been years since I played pool, but I don't ever remember seeing that before.
Should have carved in a name on the back of that chair. :)
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On 12/22/15 5:12 PM, OFWW wrote:

Me, too! That is very cool.
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On 12/22/2015 6:12 PM, OFWW wrote:

The Spectator chairs for pool matches are known as the "Electric chair" because as long as you're sitting in it, your opponent is kicking your ass, IE, killing you. I thought about that but I don't carve and it was just a prototype.
As far as the notches for the cue stick goes, that's common for this type of chair, however, when I made the holes, using a forstner bit, I should have made it easier for the cue to release from the hole. As it stands, some drunk must have tripped on a cue in one of the slots, and broke off the a small piece of the arm. If anyone makes a similar chair, keep that in mind. You don't want the cue to slip too easily out of the notch, but then you want it to come out easily if some ass trips on the cue.
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You're probably right. I have it in my mind that that was tested, but it was probably somewhere else and I'm conflating two different articles.

This is exactly what I was thinking.
John
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From the FWW Issue 203...
The test was for diagonal compression (racking force.) All results in pounds. Half lap 1603 Bridle           1560 Splined miter 1498 3/8 M&T 1444 3/8 floating M&T 1396 Miter 1374 3/8 wedged M&T 1210 3/8 pinned M&T 1162 5/16 M&T 988 Beadlock 836 Dowelmax 759 1/4 M&T 717 Pocket screw 698 Domino 597 Biscuit 545 Butt 473 Cope & stick 313 Stub tenon 200
There ya go...
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On 12/22/2015 5:45 PM, Larry wrote:

If I am reading this correctly a Butt joint was shown to be stronger than a stub tenon and cope and stick...
Bonjour!
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Well, cope & stick and butt joint are both long grain to end grain (since they were doing right angle joints). I'm going to guess (since I still haven't found that issue) that their butt joint had a lot more glue area than their cope & stick joint.
No idea why the stub tenon did so poorly.
To Jack's point, I'm going to guess that all our experiences say any joint over 750lbs-force or thereabouts is ample for most any use we're going to put it to.
John
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On 12/23/2015 9:08 AM, John McCoy wrote:

Well not really, all things being equal. My cope and stick and stub tenon joints typically have a minimum of double the glue surface area than a simple butt joint.

If it is too shallow it could be a problem but mine are always 1/2" deep so I am getting 1.75" square inches of glue surface area per linear inch.

they interlock they also self align. With plain butt joints and or pocket hole screws you have to be cautious that the outer exposed surfaces of the joint end up on the same plane.
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On 12/22/2015 6:45 PM, Larry wrote:

That's interesting stuff, but, I have some serious questions on some of it, most of it the more I look at it. For example, a floating M&T is way, way stonger than a Domino? I thought a domino WAS a floating M&T??? A splined miter is really strong, I don't think so. A butt joint is not even really a joint, imo. A butt joint needs dowels, pocket screws or something to make it a joint. Gluing two pieces of wood together with end grain doesn't work, so what on earth were they talking about? A 3/8 M&T is a stub tenon, and pretty much a cope and stick, for the most part, so again, it's not clear to me what they are doing. A miter joint is stronger than a domino? Really? A miter joint is the weakest joint I know of, other than a butt joint.
Can't wait to see what Leon thinks of this list, particularly the domino joint being near the bottom of the list. Hogwash I say:-) Who made this list, Scott Phillips?
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On 12/23/2015 12:09 PM, Jack wrote:

It's on the Internet, it's got to be true, eh?
AAMOF, Leon already made his feeling known with "Bonjour". (think: French Model)
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Jack wrote:

Actually, it can work pretty well. With thickened epoxy.
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On 12/23/2015 12:09 PM, Jack wrote:

I thought a domino WAS a floating

My thoughts exactly Jack, a Domino is a floating M&T.
In fact a Domino or floating tenon may ever be better than a plain M&T. Often the end of a board that you are going to form into a tenon might not be suitable if it has a knot or strange grain.
A splined miter is really strong, I don't think so. A butt

SCMS a RAS.
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Well, as I recall the article (and as I posted above), the two joints broke in different ways. The M&T, all varieties including floating, sheared the tenon. The domino (and dowelmax, etc) all broke the mortised board.
I have no idea why that difference would exist, and I don't recall that the article went into any analysis of it.
It does seem to me strange that the mortised board should break at a much lower strain with the domino than with a floating tenon (where the mortised board didn't break at all).
John
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Following up to myself, I found the article on line:
http://paul-flores.com/downloads/Joinery_Failure.pdf
replete with pictures of the failed joints.
I was mistaken in thinking they didn't speculate on the different failures - it seems they attribute it to the domino, etc, being shorter than a typical tenon. Which I guess would depend on exactly what you were trying to join, but in their test pieces was the case.
John
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On 12/23/2015 2:43 PM, John McCoy wrote:

The fact that the Butt joint scored higher than two other methods makes the whole article suspect. I would not be surprised at all if the chart was sorted but not all of the columns were included in the sort. LOL
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