It seems to be the case in all of the experiments available on the
Internet that the premise, "stronger than the wood itself", means that
the tester accepted the fact that the wood failed, not on the
glueline, but in an area adjacent to the glueline. The test panels
all had a single glue line and the force was applied to the center of
the panel / glueline.
In the real world what we worry about is that there will be wracking
forces around the perimeter of the panel where it is enclosed by the
I would propose to create two series of three test panels that have
four glue lines / joints in them. Two glue lines will use biscuits
and two will be rubbed and butted. The panel will then be clamped and
allowed to sit overnight.
The critical difference in this test will be that the force is applied
to the center of the panel and that no joint will be any closer than
two inches from the centerline of the application of force. In other
words. the force will be applied to undisturbed wood, rather than
directly on the glue line.
The second test will apply stress to the edges of the panels,
mimicking the forces of a wracking panel against an unyielding frame.
Now, I only have a bathroom scale available to measure the force but
that should be enough to prove the thesis, or not.
Thos. J. Watson - Cabinetmaker
The geometry is such that the bending moment is maximized at the
midpoint between the support points -- that's fact.
Anything that causes it to break in another location is either a weak
point in the material or a flaw in the joint.
That they don't (typically) break along the glue line is proof positive
the glue bond is at least as strong as the mean strength of the wood.
The test has been done both scientifically and empirically enough that
there simply isn't any doubt of the general principles in play here...
In an informal test environment the variability in the test itself will
probably negate much chance of proving anything conclusive unfortunately.
$0.02, etc., etc., ...
On Wed, 6 Aug 2008 22:11:28 -0700 (PDT), " email@example.com"
<snip tech info>
When I got my first biscuit jointer, I did a few experiments with it... just
curious if the things were any good..
I built a couple of different size frames out of 1x4 scrap, using biscuits and
Titebond for assembly..
I let then sit for a week or so and them started flexing and bending them until
a few joints failed, and every joint that I managed to break had the wood
breaking and the biscuit still glued in place on both boards..
I have no scientific basis for the holding power, but it impressed the shit
BTW: Robert, WTF is a literati?
Somewhere back here in the archives I put on the data on my home
tests. Like you, I had to see. I had been using my biscuit machine
for a while, and liked it a lot, but in all honesty never battle
tested the joints I made using them. I read some of the opinions that
started cropping up on Woodweb, Woodworkers forum, Sawmill, etc, a few
years ago (amazing how many copy and paste from forum to forum) about
the lack of integrity of a biscuit joint.
I was using my BJ in my business, and got a little shaky in using it.
I sure didn't want to go back to dowels for connectors. But the bane
of any service business has to be warranty. I couldn't stand the
thought of a lawyer's bookcase (remember when we all had to build
those damn things?), built in cabs, or anything else failing.
As time went on, more and more piling on came about with the "biscuits
are useless" tribe. Based on nothing except what they had heard on
another forum, it was one of the more well traveled stories of the
internet. I finally got nervous enough (and biscuits are SOOOO cheap)
that I had to do some testing of my own.
I edge glued 2x12 pine from left over shelving together. One test
group had no biscuits, the other had biscuits every 4 inches. I let
them dry, and place the them parallel to my sawhorses with the long
edges riding on the sawhorses and the joint in the middle. I stacked
weight on them until they broke.
True enough, neither broke at the glue joint, but the un-biscuited
joint failed with significantly more weight on it. I could only guess
that it was because (from observation) the one without the biscuits
flexed more than the other when under stress. I only did that one
test and seeing how strong the biscuit joint was, I was relieved. I
wanted to try it with hardwood, but that stuff is now and always has
been gold around here.
So... since filling 4d nail holes in the stiles of cabinets are always
a pain, and sometimes obvious after finishing, I decided to glue
stiles on with and without biscuits on test piece of cabinet plywood
to mock up a carcass. When pulling the 1X2 away from edge of the
plywood, there was <significantly> better hold with the biscuits. But
the biscuits pulled out hunks of plywood after a pry bar was used. I
was happy knowing that my clients would never take a pry bar to the
But where the biscuits on plywood really did their stuff was when I
try to shear off the 1X2 in a motion that was perpendicular to the
plywood. Now good sir, that was some real holding power. Hercules
would have had a good time with that.
My test results were like yours. Properly glued, properly set, etc.,
I was actually surprised. Then (sure wish I had it now!) I ran across
a university study that compared modern joining methods. If you want
to see a kick ass joint that will hold up well past any expectations,
double or triple the biscuits. Wow. They tried biscuits v. dowels,
biscuits v. mortise and tenon (like the link I posted) and some
others. It was obvious that the biscuit joiner had great value.
Triple biscuit that 2X4 test miter you did and try to tear them apart
after drying. Then you will see how much holding power those little
bastards have. This is also amply shown in one of the graphics on the
But I think it is important to remember, like today's Domino, the BJ
came about to allow a woodworker (probably a professional since they
started making them in the 30's or 40's in Europe for the furniture
industry) to make fast, accurate joints. The joints made with this
machine were not made to replace a welder, 10" lag screws in 8x8
posts, or other types of joining methods.
To me, the beauty of the biscuit joiner is that it takes no time to
master and it makes accurate, repeatable and durable joinery fast and
easy to do. I have literally never had a biscuit joint fail. If they
did, I didn't know about it.
That includes edge gluing as well. I don't believe that something
that works as well as it does with so little hassle for certain joints
doesn't bring >>anything<< to the project except alignment reference
But I was worried enough to spend a few off hours testing for my own
satisfaction. I have never heard of most of these 0.03 a word
computer jockeys that write these contributing pieces and simply don't
trust most of what I read in their respective bird cage protectants.
Besides, when I had to lab test my biscuit joiner I had been using it
for about 3 years or so and had just bought another 1000 biscuits!
I was almost convinced I had purchased a boat anchor and didn't know
It isn't the end all machine for all joining, but it has served me
very well. I don't actually use it that much, but it serves me well
when I do. It has proven to be 100% reliable.
Good for you for wood shedding that product, though! How many have
actually done that? Probably most don't have any idea what any of
their tools are actually capable (or incapable) of doing...
Well, I like Tom's answer better. Heh, heh... literato.
Anyway, to me a the literati are the folks that think they are "in the
know", the folks that have read mountains of information on a subject
or two and deem themselves "experts" of sorts. In the case of those I
was referring to, rarely do those "in the know" have much hands on
experience, nor do they have any practical usage time to support their
Yet they will argue endlessly to defend their point of view simply
because they know no better. But being well read on a subject, they
feel like they know a lot about it, so therefore they are an expert.
This applies to just about any subject, BTW.
In this case, I would wonder how many of the folks that have repeated
over and over that biscuits are just alignment tools have actually
used one for anything more than a weekend bookcase or coffee table.
Every time I see the alignment tool myth start up, I think of Homer J.
(Think of a whining voice) "Ohhhh.... but Marge, it HAS to be
true.... I read it on the internet!"
In the specific context of panel glue-ups, (or even face frame to
cabinet joints) do you think that biscuits are more than alignment tools?
I'm no expert, but from everything I've read and researched, glue alone
should be plenty strong in both of those cases.
For miter joints, edge-to-face, end-to-face, end-to-end, etc. I fully
agree that biscuits can add significant strength as compared to glue alone.
No question about that ... it is most often _all_ you need ... if that is
all you're after.
Do the following with regard to edge to edge panel gluing:
1. Lay out your panel boards side by side, with no biscuits and no glue on
Now try and pick up all boards at the same time and notice, other than
friction, and for all practical purposes, there is no "joint strength"
2. Lay out your panel boards side by side, with biscuits, but no glue on
either the biscuits or the board edges.
Now try and pick up all boards at the same time and notice that adding the
friction attributable to the glueless biscuits in their slots has added a
small, but measurable amount of "joint strength" over 1 above, particularly
in shear strength, which is one of the ideal components in a joint of this
3. Lay out your panel boards side by side, this time with biscuits properly
glued in, but no glue on the board edges.
Now try and pick up all boards at the same time and notice, after sufficient
clamping/drying, a relatively significant amount of increase in "joint
strength" over 1 and 2 above.
4. Lay out your panel boards side by side, with biscuits properly glued in,
and with glue properly applied to the edges. After sufficient
clamping/drying, measure the joint strength.
Now tell me, with a straight face and clear conscience, that steps 2 and 3
added NOTHING in strength whatsoever to the final "joint strength" in 4!
Granted, you may not need it, but it won't hurt and it just may be there
when you do (and easy/cheap insurance for those who prefer a belt and
suspenders approach for posterities sake).
That said, there are other reasons for adding biscuits to a panel glue-up,
other than "alignment" and the arguable possibility of added "joint
Joint "creep" .. which, IME, is particularly noticeable in wood cut off the
log in a manner that much of the dimensional instability is reflected in
movement in thickness (as you often experience in quarter sawn woods),
instead of across the grain width.
IME, there is a noticeable decrease, over time, in the effects of this
phenomena when using biscuits in panel glue-ups.
Hell, I'm tuned in. Chris, you're surrounded!!
All in good fun sir, but with a lot of good info attached.
Well, that would be me. I am not as bad as I used to be, but I think
somewhere in my old German bloodline there must have been some
woodworker that was convinced it was only worthwhile to build things
for the ages.
After I started paying for all the extra fasteners, glue, materials
and time on the project to get it "right", I decided to trust some of
the old ways. Not completely, though.
I can't quantify how much, but it seems that way to me as well. I
have built display cases (hey... who could afford a 1X24 piece of
black walnut?) that were constructed in different styles. One guy
that still has his where I can see him when I go to his office only
has one tiny line that raises about a thousandth or so when they keep
the building closed up for a holiday with the AC turned to 82.
When it is in the AC at 73 (the normal temp) it moves back into
Earlier efforts that are in the hands of family don't necessarily fare
as well. I made a coffee table from edge glued 1X6s from soft pine
and it held up well for a few years. Yet continued use caused the
joints to fail. Not completely, but they did open up.
Subsequent efforts to make country style coffee/tea cabinets to pay
for gas when I was struggling as a carpenter worked better than no
other support. I would cut down a piece of wood to 3/4" X 1" (saw
this on a piece of furniture at an antique show) and lay them
perpendicular to the edge glued wood and glue them on, nailing with a
My sister has one of those cabinets left, and it doesn't move at all.
But it was a lot of work for longer layups. I HATED doweling edges as
even with my cute little gizmo I couldn't get every single dowel to
line up perfectly.
I tried the biscuit joiner after a friend of mine that built furniture
got a Lamello and loved it. Next project I needed to do a big glue up
on, I used it and have found a lot of uses for it since.
I was a latecomer to the use of plate joinery, and the upshot of it is that,
a few years back, one of the folks who was personally instrumental in
convincing me of their worth was ... none other than Tom Watson himself. :)
I had been using splines only to reinforce miter joints and Tom convinced me
that biscuits were quite acceptable for the task. I've been thankful for
that advice every since.
I'm sure it's in the archives somewhere.
Honestly, I have never, ever wondered how to cut things that close.
Never had any interest in that kind of horsecrap, and don't want to
learn. I am not interested in cutting "that fine line" of cost v.
I don't like any kind of warranty work, and I am pissed off if I get a
warranty call on any aspect of our work.
If it is for work I personally did, I am in disbelief. I have a great
track record because I take the extra steps, and if I need to spend a
little more time and effort to get the job I want for the client, I
will spend it out of my own pocket if I have to. Not my first
preference to pay extras myself, but I just hate sub par work. I hate
warranty calls (embarrassing and costly) more than just about any
aspect of business, just behind my taxes.
I am known to tell my clients "well.... I know what you are saying,
but I am find this hard to believe. Why don't I slip by a little
later and I'll look at the XXXX together?" I am better than I used to
be (mellowed?) and don't get indignant right off the bat.
I know for many here this is something they have heard as much as I
did when I was starting out: Do it right the first time and forget
about it. Go on to the next project.
This hits on Swing's point. Why not? Why not take the extra few
minutes to be dead bang 110% sure of your work? It makes me proud and
confident to know that I did a good job.
It is good to be the guy on the phone with a little disbelief in your
voice when someone tells you there is a problem with your work. It's
better to be able to back up your disbelief when you see what the
"problem" is when you see it.
Before anyone starts in here, I am not saying I am perfect and not
every single job gets my undying effort. But my goal is to make my
work is as good as I can make it (within reason) before I turn it
over. I make sure my client gets 110% of what they pay for.
Belt and suspenders? Yup, that's me.
On the other foot, I periodically go through "3rd party inspections" prior
to closing on houses we build. While I welcome them for the most part, I
still find it about as _personal_ as a term final/paper in college, where no
matter what you did good going in, the results of the one shot deal, and for
all the world to see, is all that counts.
Sad thing is that most of the inspectors know less about good building
practices than I do, but _I_ must still defend/justify every "issue" they
come up with, right or wrong ( and all too often these days, the latter ...
you won't believe some of the crap these "licensed professionals" are
capable of) ... IOW, it ends up being a matter of personal pride and damn
hard not to take it any other way.
If I could build a house by myself, the way I work in my own shop, fine ...
but you can only "supervise" so much and the culture that builds today
doesn't give a warm bucket of spit about pride of workmanship, meaning you
constantly have to accept things you personally cringe at to get anything
accomplished ... to do otherwise is financial suicide, won't help you, your
family, your kid in college, or even the folks buying the product (who,
these days, mostly don't know the difference, or even give a shit).
About the only relief I get from this constant barrage of crappy workmanship
is in _my_ shop, on _my_ projects, where I have control over the amount of
"pride of workmanship" that goes into it.
Which is one reason why I have such a great deal of respect for guys like
Leon and Tom, who have reached a level where they can carefully pick and
choose jobs where the exercise of that option is a given.
One of these days ...
I actually liken it to a prostate exam - done by a retired plumber.
It used to be the case around here that when builders (carpenters)
retired they would go into the inspection game. That worked pretty
well and I learned a lot from those old boys when I was growing up.
Nowadays we get pissants who have studied up the UBC and think they
know jackshit about building. They ain't worth a damn.
What's funny is, we have about four townships around here that I work
in on a regular basis. Most of the inspectors I know by name and
sight. I also know that each of them have certain hardons. One guy
is a killer on the height between the first stair tread and the
ceiling line that is vertical to it. Another guy is all about
firestops (volunteer fireman). A third just wants to make sure that
all the air passages have been sealed (anal retentive). The last guy
is a shooting buddy of mine and just wishes that accountants would not
try to design buildings.
I feel your pain, brother. When we throw the system into reverse for
a minute and understand that a young man who wants to spend his life
working with his hands is not to be treated as a retard, or someone
not worthy of the same level of respect as a white collar office
drone, we will begin to have something again.
Thank You. I appreciate being included in the same breath with Leon.
I have great respect for he and thou and wish that we could all work
Thos. J. Watson - Cabinetmaker
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