Walnut and Glue

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I've done a bit of glue-ups. Most have been successful. Some have been disastrous, but with each failure, I've been able to figure out what I did wrong and not repeat it too many times. All have been with pine, maple, or oak.
At this point, the glue-ups I find easiest to do are laminations or edge gluing. If the surfaces are clean and planed smooth, and the clamping pressure is enough, the joint will hold for me.
The other day I went to the kindling pile to get some wood for turning a knob. I didn't have the size I needed, so I decided to take 2 pieces and face-glue them together to give me the thickness I needed. I'm fairly sure the pieces were walnut. The glue was Titebond III
The first two pieces fell apart by hand. I was in a hurry and used weak clamps. I also didn't wait long enough for the glue to bond.
The second two pieces went better but fell apart when I was turning on the lathe. Same for the third set. Both of the second sets had much stronger clamps and I waited a full day.
In all cases, the faces were flat and smooth, planed by hand.
What am I doing wrong?
Tanus
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Well, Walnut has nothing to do with it. The glue may not be fully cured and with a joint spinning and pulling it could fail if not properly cured. Walnut is NOT incredibly strong, did the joint fail or did the wood fail close to the joint?
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Leon wrote:

Sorry guys.I should have given more information.
All joints failed at the glue. In other words, the pieces pretty much fell apart with no wood breaking.
The glue hasn't frozen but it has been cold. I've used the glue recently and it's worked fine. Although I keep the glue in an unheated shop, the cabinet it's stored in is heated throughout the winter. Buying new glue is what I'll do next.
I liked the idea of staving the joint until more than a few of you said that likely wasn't the case, which is bringing me back to bad glue.
The faces were hand planed and very smooth to the touch. No sanding after planing. I squeezed the glue in a zig zag along both surfaces and then smoothed with a finger so the glue was even on both.
There is some doubt in my mind about the wood being walnut. I'll verify that later. However, the wood from the kindling pile was very dry. I get my kindling from a cabinet shop locally, and store it in a shed before and after sawing it to length.
I'll get some more glue and try this thing again. In the interim, I made my knobs from other stock, but this idea of glue failing is not one I want to repeat.
Thanks all of you for the replies. I didn't think this was going to generate so much. I'm glad I asked.
Tanus
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On Tue, 27 May 2008 18:33:50 -0400, Tanus

Howdy,
'Just curious...
How do you heat the cabinet?
Thanks,
--
Kenneth

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Kenneth wrote:

Hi Ken,
I can't remember what these things are called, but they're sold as copper line heaters to prevent the water line from freezing. I got mine at the Borg. 120 volt with a simple bimetallic strip thermostat. They look like extension cords and give off enough heat to keep the line from freezing but are not too hot to handle with bare hands. Lengths vary from 6' to 25' or more.
I've lined a cupboard with Styrofoam SM and put a couple of these line heaters around the perimeter. It keeps the cabinet warm enough for my glues, water stones and anything else I need to keep from freezing. The rest of the shop can get down to about -30 C but the cabinet stays above freezing.
Tanus
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"Tanus" wrote:

Where I come from they are known as heat tapes.
Lew
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Tanus wrote:

Some woods such as Hond. cherry have oil in them and the surface needs to be wipe with Acetone just prior to gluing, otherwise it will just seperate as I found out.
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^^^^^^
Using your finger to smear the glue might have something to do with your problem. It could be that whatever oils are on your hand don't mix with the glue. Try using an acid brush to smooth the glue around next time and see if that makes any difference.
[1]: http://www.harborfreight.com/cpi/ctaf/displayitem.taf?ItemnumberA338
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Tanus wrote: ...

Well, that's obvious enough...

I don't really have a clue -- a glue joint of that type should be possible to make hold stronger than the wood itself simply w/ a "rub fit" even w/o clamping at all.
I have only a few guesses (and they're all simply that w/ no more data or observation)...
1. The source of the material from the woodpile makes me wonder--was this dry lumber or scrap firewood that could possibly be wet? Seems unlikely, but we're searching here...
2. The glue is old or your simply not using sufficient amount to get good glue surface. Since same symptom w/ "weak" or "stronger" clamps, I'm assuming you're not clamping to the point of glue starvation, but that's another possibility.
3. Surfaces aren't very flat or are excessively burnished so no porosity for glue. Would be very difficult w/ walnut given it's open-pored characteristics but again...
I can think of very few glue joints that didn't hold ever over 30 years and virtually all of them could be attributed to either trying to make ill-fitting pieces stick or pushing the envelope of temperature (cold) on the glue.
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dpb wrote:

Too much pressure will result in a glue-starved joint. I think many people go overboard on the clamping pressure with Titebond and the like.
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I read some research that proved this to be an old wives tale. Joints can be glue starved, BUT not at the pressure generated by hand clamps. The study was scientifically done and reported in a woodworking mag.
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snipped-for-privacy@nycap.rr.com wrote:

That would have been Fine Woodworking (about 3-4 issues ago?).
Pretty incredible recommendations in it--if followed, we'd all need hydraulic presses to meet the "optimum" clamping pressures... :)
Fortunately, experience has shown that far less clamping pressure than those determined by the research reported therein is adequate for highly reliable joints.
The likelihood of glue starvation by clamping pressure would be quite low for OP's case I would think except for two possibilities that seem present in his case--possibly not using sufficient to start with and a small glue joint area means clamp pressure is concentrated and if he was concerned in not clamping enough, could possibly have really torqued down. Don't know what kind of clamps were used, either, of course...
The possibility posted elsewhere of the glue having been subject to freezing over the winter is a most excellent one I hadn't thought of...that would do it.
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snipped-for-privacy@nycap.rr.com wrote:

For certain values of "scientifically". And hardly "old wives tale" when the glue manufacturers agree with years of serious research by the likes of Forest Products Laboratories that for each type of glue there is an optimal glue line thickness, the achievement of which depends on the type of wood, the grain orientation, the viscosity of the glue, and the clamping pressure.
As for "the pressure generated by hand clamps", how much pressure is that? That depends on the joint geometry. Don't confuse "force" with "pressure".
One test reported in the popular press is not definitive research.
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J. Clarke wrote:

Yep. And for hard maple and PVA the optimal glue line thickness resulted from very high pressures...substantially more than the 250psi that is at the upper end of Franklin's recommendations.
However, as "dpb" mentioned, optimal is not normally necessary, and quite adequate joints can be made at much lower pressure.

Absolutely true. Common misconception.
Chris
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Chris Friesen wrote:

If one needs "very high pressures" to achieve 3-6 mil bond line thickness then one is applying too much glue. Note that the table of "recommended clamping pressures" in the Roman Rablej article in Fine Woodworking appears to have been pulled out of Rablej's ass. He gives no source for it at all.

Which is beside the point.

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J. Clarke wrote:

It may not be the case that a 3-6 mil thickness is always ideal. If so, then higher pressures may be better.
As "dpb" mentioned in this newsgroup when the FWW article came out, I'd guess the pressures came from Rabiej's paper:
"The Effect of Clamping Pressure and Orthotropic Wood Structure on the Strength of Glued Bonds", Wood and Fiber Science Vol. 24, No. 3, July 1992.
From the abstract at "http://swst.metapress.com/content/1050536165217317/?p 5006db06be4640acd2801679e46c4e&pi=3"
"...Using this concept, the optimum clamping pressure for sugar maple was found to be 0.3 times compression strength using U-F glue and 0.5 times using PVAc glue. This approach to determining reliable clamping pressure data can lead to improved gluing practice and more precise testing procedures."
Using the FPL tables, this gives a bit over 700psi for PVA glue.
Chris
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Chris Friesen wrote:

Do you have evidence that it is not?

How about just applying the right thickness to begin with instead of glomming it on and trying to squeeze it out with clamps?

"http://swst.metapress.com/content/1050536165217317/?p 5006db06be4640acd2801679e46c4e&pi=3"
But (a) how much difference does he see (I'm not really interesting in paying 25 bucks to find out) and (b) has anybody replicated his results?
Personally I'll take FPL's recommendations based on decades of experience backed by research over one unreplicated paper.
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J. Clarke wrote:

The guy is a prof in industrial processes at a university w/, it appears, something like 20 years or so of experience and a fairly long list of published and contract works from various sources including FPL and wood manufacturing businesses. From that, I would presume his work has been considered valuable or he wouldn't continue to hold the position and find clients.
OTOH, it does appear that his work is mostly for large, automated industrial processes so that I think his results aren't of great import to most small shops or individuals as is the general readership of r.w nor do I think most of FWW's readership is of the same type/style of manufacturing as that to which his research is/was directed.
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Correct.
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No, it will not, that is an old wives tale. The only way you get glue starvation is to not apply enough in the first place or scrape it all off during insertion. A mortise and tennon joint that fits too tightly can scrape all the glue off during assembly.
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