Jointing or Biscuits

Ain't that plural for literature? Hippopotamus, Hippopotami. LOL

Reply to
Leon
Loading thread data ...

Thanks very much for all advice.

Arthur

Reply to
Arthur2

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 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 cabinets.

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 supplied link.

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 I have no scientific basis for the holding power, but it impressed the shit

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 opinion.

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. Simpson.

(Think of a whining voice) "Ohhhh.... but Marge, it HAS to be true.... I read it on the internet!"

Robert

Reply to
nailshooter41

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.

Chris

Reply to
Chris Friesen

"Chris Friesen" wrote

Depends ... not "one size fits all" situations.

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 the edges.

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" whatsoever.

  1. 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 type.

  1. 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.

  1. 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 strength":

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.

YMMV ...

Reply to
Swingman

It wears me out just reading the instructions, much less perform the experiments

Lew

Reply to
Lew Hodgett

No pain, no gain. :)

Reply to
Swingman

let me ask you a question, Chris.

In all the tests that I have seen, although it is true that the glue line does not break, the break is always near the glue line. It does not appear to be the case that the break is in another part of the panel that is away from the glue line.

What's up with that?

Regards, Tom.

Thos. J. Watson - Cabinetmaker

formatting link

Reply to
Tom Watson

There you go, Arthur. You now have the answer. I would like to add, that cheapo biscuits often have random grain orientation as opposed to a diagonal to the oval shape, like 'select' biscuits such as the Lamellos. If a biscuit breaks along its length in your application, it would add less strength than if it was inclined to break on the diagonal. The change of grain direction along the stress line, adds strength.... assuming that the biscuit was installed properly, i.e. the slot (pocket) wasn't unnecessarily big. You want to take away as little of the original material as possible without running into a hydro-locking condition.

I have used thousands upon thousands of biscuits and conducted many tests and read/archived many such tests. The DO add strength to a joint, and in certain properly executed applications, can get close in performance to a floating tenon.

The drawback, of course, is that when you use biscuits to make a panel, you can see the telegraphed shape of the biscuit after you sand and finish the panel.

r->Zebco 6, 4' graphite ultra-light.

Reply to
Robatoy

Tom Watson wrote: ...

...

Every test I've seen the two pieces are the same width so the joint is in the middle. When the board is loaded and supported on the edges, the point of highest stress is then in the middle; hence unless there is a weak point farther towards one edge or another, the most likely place for the failure is near the point of highest stress, the middle.

Since as noted, the glue joint actually is generally as strong as or stronger than the material, typically it is slightly to one side or the other of the joint where the break occurs.

Simply physics of the test geometry is the basic explanation... :)

The more interesting test that is illuminating is the one of the bridle joint joint loaded perpendicularly to the grain on one piece -- even there it is typically either the wood that breaks or a combination rather than a glue-line failure for well machined joints.

Reply to
dpb

A little ancient history from our own resources.

Please note the concepts of grain direction and the relieved shoulders.

"This history on the development of the plate joiner system was originally posted to rec.woodworking on February 12, 1988 in response to a discussion comparing the strength of biscuits to dowels. The author is Sherman Whipple, who has graciously allowed the republication of his exposition on the development of the plate joiner system.

There is an elderly gentleman by the name of Herman Stiener who lives in Switzerland. He would probably get the greatest kick from reading all the threads about biscuits vs. dowels, tenons, etc. You see it was Herman Steiner who started this whole thread back in 1955, two years before there even was an Internet and after 43 years, it is still going on; he's the guy who invented the things.

He also adapted a right-angle grinder to invent the first gadget to index the slots, as well. He also made a neat clamping system, defect patcher, and quite a number of other woodworking devices and techniques. Mr. Steiner was by profession an engineer, and from what I have been told was quite good at it. Cabinetmaking for him, as for most of us, was just a hobby. He invented it in his home workshop.

The design of the joining plate and the secret of its strength are based upon very sound engineering. For example, wood's greatest strength is against the bias. We all know it is weakest with the grain, but most of us assume that it would be strongest across the grain: wrong. It is strongest with the grain angled 45 degrees and beech is one of the strongest in this orientation. One would also imagine that a rectangular plate would add greater strength than the football shape. In dealing with wood, however, if the base of the slot were square, as in a long spline with the grain, the wood would be weakened. The elliptical slots prevent splitting. Basically the design of the plate provides the maximum spreading of the load and a better glue surface. The addition of the compression and swelling properties and the tread pattern to open the wood fibers all came later.

It is my understanding that when Herman began to share his invention he was met with considerable disbelief from the local cabinetmakers. To prove it, he would have them make a couple of simple "T" joints. One with the technique they thought would be strongest and one with his "lamellae" which means thin plate. After the glue had set he would challenge them to break the joint. Every time, the plates won the challenge. Every cabinetmaker became a customer and he started a business to make plates called Steiner Lamello. Soon after he introduced the indexing base and then the first dedicated plate-joining machine.

The first Lamello machines did not begin to appear in the US until the mid-to- late 1960's, but it was not until about 1977 that they started to see wide acceptance. This was mostly in industrial applications. The rest of course, is history. We don't know who invented the wheel, or figured out how to cut the first dovetail, but we do know who made the joining plate, biscuit, lemon spline, or Lamello. It was a guy just like us by the name of Herman Steiner.

Sherman Whipple

Whipple, Sargent & Associates Strategic Services

37 Derby Street, Suite 7B Hingham, MA 02043

Phone: 781-740-4025 Fax: 781-749-9474

E-Mail: snipped-for-privacy@whipplesargent.com

For more information about biscuit joinery see:

formatting link
"

Regards, Tom.

Thos. J. Watson - Cabinetmaker

formatting link

Reply to
Tom Watson

Somewhere in this thread, are my personal results from just such a hypothesis that was put to experiment.

My personal results completely agree with the tests you have seen. I am no engineer so I have no great, informed answer. All I know is them's the facts, and that's good enough for me.

Robert

Reply to
nailshooter41

Tomorrow I'm going to glue up a panel like I would use for a raised panel door.

I'll let it set up for a day or so and then apply force to the center of the entire panel, which will not be the same as applying a force to a single glue line.

I'll be interested to see what happens.

Regards, Tom.

Thos. J. Watson - Cabinetmaker

formatting link

Reply to
Tom Watson

My suspicion is that the very act of gluing creates a weakness in the wood fibers close to the glue line.

It's like a woodworking application of the uncertainty principle.

Regards, Tom.

Thos. J. Watson - Cabinetmaker

formatting link

Reply to
Tom Watson

Please do not respond to me with posts that explain the workings of the actual uncertainty principle.

It was an attempt at humorous analogy.

Regards, Tom.

Thos. J. Watson - Cabinetmaker

formatting link

Reply to
Tom Watson

SNIP of great stuff

I don't know how or where you found that or if you took the time to type it from your archives, but thanks for posting that piece.

Neat stuff.

Robert

Reply to
nailshooter41

I did a search for "lemon splines" which was the old name for biscuits.

When I was a young fella a lemon splined joint in the corners of the door casing was taken as a mark of quality, and also an indication that the trim had been run up in a cabinet / millwork shop prior to its arrival onsite.

Regards, Tom.

Thos. J. Watson - Cabinetmaker

formatting link

Reply to
Tom Watson

...

:)

Being a nuclear engineer/physicist by training, I'll refrain (w/ difficulty)...

The actual is owing to the general test layout and the physics of plate bending as noted in an earlier thread. If the material were actually entirely uniform as we all know wood isn't, the bending stresses would be perfectly symmetric and a solid piece of the same dimensions would bend then break right down the middle.

There's a small effect at the edge owing to the discontinuity of the fibers across the joint but w/ reasonably straight-grained wood it's a secondary issue. The glue joint is, in fact, stronger than the breaking strength and which side the test sample breaks upon depends on which board has the weaker point flaw assuming even loading.

If you look at some of the web sides that have the "sagulator" calculators for beam loading, some of them also have stress/strain curves associated with them for various loading patterns. For simply-supported ends and point load in the middle, the bending moment diagram is linear from the endpoints to the middle, then decreases in the other direction to zero again at the other edge. Something like

Load | \|/ ------------- Beam/panel

\ / -- 0 (zero bending moment) \ / \ / \ / \ / \ / ------ M (max bending moment)

--

Reply to
dpb

SNIP of the second Manhattan project

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 place.

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 million 4ds.

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.

Robert

Reply to
nailshooter41

I am mindful of your explication.

My point, and I would say, my premise, is that the act of gluing introduces some deterioration to the fibers along the line.

The test that I have planned should be interesting in either proving it out to a degree that it becomes a theory, or putting the idea to bed.

I would be disinclined to bring Heisenberg into this discussion beyond saying that every time that I would try to look at my experiment the parameters would change - and that would piss me off.

Regards, Tom.

Thos. J. Watson - Cabinetmaker

formatting link

Reply to
Tom Watson

HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.