As I said in an earlier response, "the results have no bearing as a
general rule; they _only_ represent the actual joints as tested".
Of course a Domino is a floating M&T but you can see precisely why the
two are so disparate in results in the test and in the order they are if
you go look at the pictures. While the actual dimensions of the F-M&T
in the test aren't given, it is obviously at least twice the width of
the (single) Domino used giving it 2X the surface area each side plus
twice the vertical dimension from the midplane (vertically) to resist
racking force mechanically.
As so much of the other discussion, it's obvious just looking that it'll
win; precisely how much I'd have guessed at the roughly 2X factor shown.
The problem with both the cope and stick and stub tenon in this test is
there's no material left on the sides of any significance -- look at the
failure mechanism, it split the two skinny sides while the glue joint
remained intact. This is certainly going to be true as far as it goes,
but one would never use such a joint in the case of the example
justification in the leadin for the test of wracking forces like a chair
rail; such a joint would only be found in a panel door or the like and
there the panel would be there and provide the wracking resistance.
I'll note the biscuit suffered a like fate--the glue is so strong it
simply fractured the two remaining long-grain sides of the slot in the
stile as their cross-sectional areas are so small given the depth is,
like the stub and cope, so short there's no area over which to dissipate
the concentrated tension force. That's the reason (besides that the
tenon itself has bending moment resistance) the M&T does well, there's
the full depth of the tenon over which the force is spread.
I think if one were to do similar actual geometrical comparisons of the
rest there would be clearly recognizable reasons for them as well.
It's a case of comparing things that for the most part, shouldn't be
compared in the overall rankings; only the minor differences between the
similarly-sized and purposed joints should actually be compared against
each other within a set of classes, perhaps.
Well, the counterpart to what you just said is that you should
consider the size of the joint when picking your joinery method.
If a joinery method is constrained by the size of pre-fab units,
it might not be suitable.
Of course, that's assuming you need maximum strength. As has
been noted several times, for most applications all the joints
are more than ample.
I said _nothing_ whatever about actual application to any specific
project; only discussing the limitation in attempting to drawing any
generic conclusions from the test results as performed/presented. See
the more detailed follow-on to 'Jack' I posted this AM.
Well, the conclusion we can draw (at least, that I draw;
you are of course free to not draw any conclusion from the
information available) is that different size joints may
require or benefit from different types of joinery.
I did see that, and don't disagree with anything you said.
Perhaps I misinterpreted what you intended the response to mean...
I think that's a foregone conclusion for the specific project and joint
within the project, yes. But I don't see that there's anything in the
article as presented that really addresses the application issue in
those terms, no.
IMO it is what is is and no more, no less--a comparison in isolation of
a set of joints prepared independently and with no (cogent) forethought
as to an actual test objective a priori. Hence it provides no
information other than the basic fact of each those test results on its own.
It would have been interesting to have seen an actual comparison of,
say, the Domino and beadlock systems under circumstances where they were
geometrically-enough similar to see if either had any advantage over the
other as a _system_ and then them as a class with respect to
conventional construction techniques. But, it's simply not possible as
the test was conducted. The closest there is to that would be within
the miter with/without splines and the M&T with its variations of
wedged/pinned; I _think_ w/o looking again at the article the latter
But, they didn't investigate haunched M&T, nor double nor the many other
variations so from a structural standpoint in aiding a particular
construction technique for a given application where true strength would
be required it's also lacking for completeness.
I think again it's another patently obvious conclusion not needing any
study at all that any/all as shown are sufficiently strong for a cabinet
door or the like that the dimensions of the two pieces joined basically
models. All in all, I thought at the time it was one of FWW's weaker
offerings, truthfully (and this discussion has only strengthened that
Anyway, I've said all I've got to contribute; think I'll retire to Santa
and the reindeer... :)
The article didn't. I was extending on your point that
a meaningful comparison would require the joints to be
the same size, to suggest out that the differing results
for different sizes indicate different joinery would be
appropriate for different sizes.
I've always been dubious that the haunch on that style
M&T contributes any strength (altho magazine writers
invariably describe it that way). I think it's only
real purpose is to fill the panel groove, and it came
into existance because a stopped groove is a pain to
make with hand tools.
I simply made a reference to it (along with several others that you
conveniently elided) that they didn't include many variations which
would be needed to be able to draw more general conclusions of relative
effectiveness of various types.
The point again being the article ranking of the various joints testing
uniformly without consideration of anything else except the one result
is simply mis-reporting the tests.
There's really no point in furthering trying to make more of it than it
This has always bugged me as well. EVERY woodworking source on earth
that mentions a haunched tenon bloviates about it's superior strength,
when anyone that ever made frame and panel anything should know the
issue is never strength, the purpose, as you said, is to fill the panel
groove. The haunched tenon might be a tad stronger as measured by a
rocket scientist, or an engineer, or any college pin head, but to a
woodworker, it's only real and meaningful purpose is to fill the groove.
Glad someone else noticed this..'
Add Life to your Days not Days to your Life.
I made no posit re: strength and wasn't implying anything whatsoever --
as noted above, John conveniently elided the remainder of the list which
again was simply that--a list--as denoting there's a "veritable
plethora" of variations that weren't tested if one were to try to use
those results to make more general judgments regarding suitability for
other purposes which seemed (to me, anyway) the direction he was trying
to take the discussion.
But, specifically, I was actually thinking of something much more like
the following application at the time I was writing the comments, not
just the simple panel-groove-filling version.
wherein there's a point in the construction itself besides cosmetics to
provide clearance and yet the largest vertical height cross-section
possible within the member.
I wasn't referring to anything you said, I was specifically referring to
John's reference to "magazine writers", as I appropriately quoted.
If you are one of those, only then would I be talking about you.
Add Life to your Days not Days to your Life.
Just to be clear, the 3/8 M&T is the tenon thickness, not
depth. The stub tenon looked to be about 3/8 deep from the
The 2 I have a problem with are the miter and butt. Both would
be at the very bottom if I were guessing.
Just reposting the results... Don't shoot the messenger.
Well, the butt is excepting for the two which again have no comparison
owing to geometry as noted earlier.
As for the miter, the 45 angle increases glue area by the sqrt(2) factor
so it's got almost 50% more for the same width pieces. Secondly, by
cutting on the diagonal, the end grain isn't _totally_ end grain so
there is a contribution of the side long grain that improves glue
performance significantly as compared to the true-90 butt.
Not shooting at you Larry. If you did the testing, _then_ I'd be
shooting at you.
Posting the list is very interesting, allowing for some banter about
joints. For me, I like Mikes points on common sense. Some common sense
and a dash of experience and this list looks a bit funny to say the
least. Swings sarcastic remark if it's on the internet, it must be
true, also is on the money.
It's amazing to me how much bull is written in books. I'm oft reminded
that the individual taste zones on your tongue was taught in schools for
over 100 years simply because one guy wrote in down in a book and grade
schools, high schools and colleges, including medical schools, taught
it for a 100 YEARS, like it was true, and was bogus.
This list in my mind is bogus, and if I were doing the testing, and
somehow a butt joint or miter joint came ahead of a domino, I'd keep it
to myself, and try to find out what I did wrong in the testing. Just my
opinion, but giant red flags here, making the whole thing suspect.
Add Life to your Days not Days to your Life.
The overall ranking is of little consequence, granted, because there's
so much disparity between the joints as far as the specifics of them are
concerned (as I've noted several times previously :) ).
Also, as far a postulating, that's well and good, but the results from a
series of tests such as this are valid _only_ for the specific joints
down to the specific sizes of the various mating pieces; one canNOT
infer anything more than that regarding general conclusions.
To do the latter would require having a series of tests of each type in
which the single variable under study _only_ is changed (say width of
the tenon in the simple M&T for one) and then _only_ tenon length. The
problem when one attempts to undertake this kind of study then becomes
one that the number of tests required explodes geometrically and rapidly
turns in to the thousands or 10s of thousands. That's where one would
then need to turn to statistical design of experiments theory to develop
a test matrix that would allow for at least some of the variables to be
studied without confounding effects(*) with a reasonable number of tests.
But, for the particular set of joints incorporated, the simple butt did
_not_ beat the Domino and there's an explanation for why the simple
miter does as outlined above.
I don't think there's anything wrong with the tests themselves such as
they were; it's simply trying to draw too many conclusions from the
results that the amount of testing doesn't support.
(*) Confounding -- when an uncontrolled or unknown variable other than
the one under test has an effect on the result of the device under test,
the result of the test cannot be shown to actually have measured the
desired effect of the intended variable. The example easily seen here
is that between the M&T, F-M&T and the Domino the sizes of the tenons
aren't controlled; only the type used. Hence, one had _no_ controls in
place for the confounding variable and there's nothing that can be said
specifically about the effectiveness of the joining _system_ at all;
only that for the three specific cases with the specific dimensions that
the results were in the order observed.
After nearly 40 yr of consulting in the area for which I coined the term
"statistical engineering", being called in after the fact to try to make
something of results from such tests as the above was all too common
what a client was wanting. Unfortunately, in almost every instance, it
was too late in the process to salvage the work done to date other than
to try to complete an actual design for a series of experiments in which
the tests run could be used to fill in the necessary test matrix.
Brings to mind large laminated beam, what if one of the variables was
mid point in the beam?
One of the questions nagging me is, the amount of pressure used on a
glued joint. Is it really possible to squeeze out too much glue and
render the project worthless a few years down the road?
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