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.
Tom Watson wrote: ...
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I don't follow that line of thought at all -- why would any _deterioration_ cause a failure away from the glue line? And what mechanism is supposedly at work doing this?
I think your proposed test (iiuc) will simply again demonstrate the point of maximum stress is in the middle of the panel and the variation in wood properties will make for a moderate difference in actual breaking point from one side to the other a la Heisenberg...
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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 frame.
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.
Regards, Tom.
Thos. J. Watson - Cabinetmaker
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. utility.
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.
Robert
Absolutely five by five on that with you, brother.
It should never be any other way.
Regards, Tom.
Thos. J. Watson - Cabinetmaker
No kidding... I haven't had that happen but once. Are you seeing this on a particular kind of wood or some size of glue up?
I know there are those that have this problem all the time, but I also know that you undoubtedly buy the good biscuits and are careful (as you cautioned above) about the installation technique.
I may not have this problem because 1) I am lucky! or 2) I dry fit the biscuits before I put them in the glue. If they don't slip in and out with just a little friction, they don't get used.
I only use the PC biscuits (I see you use Lamello) and quit using the "bag o' biscuits" when a great deal of them didn't fit right, weren't shipped properly (sealed containers) and they were crumbly.
Remember when companies like PC had actual, live tool reps, not 23 year old guys with degrees in marketing that simply filled out customer orders?
I went to a "PC Days" thing they had at Woodcraft many, many years ago and he told me their were three things that screwed up biscuit joinery (certainly not saying here that you are doing any of these!):
- Folks don't use enough biscuits (at 0.03 a whack, that one made me LMAO)
- They don't get the depth right (addressed by you)
- And they don't store the biscuits properly
According to the guy, the reason sPC went to the little clear bottles was to cut down on breakage, but more importantly keep the moisture out of the biscuits. Swelling of the biscuits was a known problem and PC apparently got a ton of them back as returns.
His opinion was that if you have to tap a biscuit in, it is too tight. He swore that tight biscuits (don't even go there, buddy... ;^) ) were the problem that caused their shape to be reflected through the wood due to their expansion when hit with the glue.
Your thoughts?
Robert
Maybe if he glued three panels, and performed the same test. If it breaks in the center of the center panel, the glue had nothing to do with it.
scott
wrote
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 ...
Not to jump in but let's remember that a properly conceived biscuit is cut in section more or less at the point between quartersawn and plainsawn.
The natural expansion properties of such a biscuit make it expand in a predictable manner that does not transmit the expansion line to the face, if the face is more than 2X away from the thickness of the biscuit, which it should always be. This holds true for both laminated and solid goods.
Where I have seen bumps in the joint line they have invariably been the result of positioning of the biscuit too close to the face, or to using poor quality biscuits.
I use an antique Lamello Top 10 and always use the Lamello plates. I bought a couple of tubes of the PC variety and found that they did not mike out to a consistent thickness. I also found that too many of the plates were flatsawn, or close to flatsawn, and that made them unacceptable.
I keep my unused plates in a container with several SilicaGel bags that help keep the moisture content down to less than 4%. I also throw in a cheap hygrometer ($6.00) to make sure that moisture is not an issue.
Your friend is right about tapping the plates in; they are no good if they need more than a gentle push to insert them.
Lamello used to have standards on their website to let you know if the biscuits had gone out of spec.
Regards, Tom.
Thos. J. Watson - Cabinetmaker
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 together someday.
Regards, Tom.
Thos. J. Watson - Cabinetmaker
Good question but I think the reason is because you are trying to break at the glue line. If you try to break some where else, the board will probably break at that somewhere else spot.
Geez Tom, I'm thinking it's the other way around. I think the 3 of us working together would be like going to heaven. Imagine 3 people striving for perfection.
I remember the movie... I think it came out in the 30s sometime. I think it was called
"The D.A. Called It Murder" or something along those lines. ;^)
No ship ever sails anywhere with 3 captains. Bet the barbecue and whiskey portion of working together would be grand to attend, though!
Robert
Yup, a team like that would need a manager.
"Leon" wrote
Actually, I was kinda hoping I'd get to play bass with SRV ... but hell, that would work too! :)
Scott Lurndal wrote: ...
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., ...
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Could anyone afford he three of you? /:o)
Dave in Houston
LOL, Well I was always a manager from the age 21 but I believe much of my success was hinged upon team work. Although I was usually the one in charge I always enjoyed being elbow to elbow with those I worked with on a daily basis. When everyone is on the same page things seem to fall into place. Experience helps a lot too. ;~)
SRV??? I'd think playing bass with LL ranks pretty high up there. ;~)
Oh~ Stevey, I'll not help you with LL. LOL
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