Glue strength -- actual numbers?

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Hi,
I'm wondering if someone knows the actual numbers on glue strength? (i.e., strength per unit of surface)
I'm talking about the plastic glue (yellow or white -- I think it's vynil-based), assuming that it is used to glue two pieces of very-flat very-clean along-the-grain wood surfaces, with no gap between the surfaces of more than 1/200" or so. At least typical values, or worst-case values (if it depends on the wood, or on the angle of the surface with respect to the grain, etc.)
A google search on this newsgroup returns nothing; the specs of the glue (both on its label and on Lepage's web site) only include the catchy advertising phrase "bonds with 2 tons of strength" (GOD, such idiots!! Only for that I shouldn't buy anything from them!!! :-( such flashbacks of infomertials advertising crap), so I'm at a loss.
Anyway, I'll be grateful for any info!
Thanks,
Carlos --
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Check out www.titebond.com. They have the PSI ratings for their glues.
David
Carlos Moreno wrote:

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http://www.franklinadhesives.com/IntroPageFA.ASP?UserType=1&ProdSel=WNPressPointCalcFA.asp . try this site they own Tite bond adhiesive.

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http://www.franklinadhesives.com/IntroPageFA.ASP?UserType=1&ProdSel=WNPressPointCalcFA.asptry this site they own tite bond adhiesives

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The LMI catalog had a short note on glue strength a few years back. I cwn't even begin to recall the numbers but I can say this much. * Shelf life will improve if kept in the refrigerator. * Shelf life is much shorter than you might suspect. * LMI offers a yellow glue with about double the strength of off-the-shelf yellow glue. The price is much higher and when kept cool the shelf life is only about six months. * Yellow glue is non gap filling. The strength comes from infusing the pores of the wood. Therefore the wood needs a smooth finish but not burnished as this will inhibit absorption. * You are correct on a gap of 1/200th inch. * Clamping pressures are much lower than most every woodworker uses. Too much pressure will result in a starved joint. * A perfect joint is much more important than one mught suspect. Never clamp tight to close a joint. Some sections of the joint will be starved, other just right, and other gap filled. Take the time to get the joint right. *Regular yellow glue (A.R.G.?) is usually stronger than the wood being joined.
That about exhausts my knowledge. Hope I was of some help.
-Rick Buchanan
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True but,

The jury is still out on this one as it has not been prooven either way. Apparently many people that clamp too hard are trying to close a gap and as indicated, yellow glues do not fill gaps well. I have never had a joint fail whether I clamped agressively or not. I choose moderate clamping pressure now.
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Not so sure I agree with the "starved joint" syndrome, merely from the application of "too much" clamping pressure. Damaged wood fibers can result from behemoth pressures, but more likely a "starved" joint is due to insufficient glue applied BEFORE clamping the joint, as opposed to the pressure of the clamping being the culprit.
David
Sbtypesetter wrote:

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overclamping can starve the joint.
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Yeah, like going swimming within 1 hour of eating will cause drowning from cramps. You are repeating a myth.
David
snipped-for-privacy@thanks.com wrote:

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If you apply clamping pressure immediately and excessively, you will squeeze so much out that you can actually break on the glue line after cure, especially on woods like hard maple which don't soak much. It's NOT a myth to an Industrial Arts teacher who's seen what teenage males can do to pipe clamps....
wrote:

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Talk to the folks at Franklin. Tell them they don't know their business.
David
David
George wrote:

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Why bother? They're probably as closed-minded as you are. Mine's by experience, can't change that.
wrote:

due
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:) I hear you George. We all have our opinions and nobody is going to change them. I'm not closed minded enough to refuse to learn "new tricks".
David
George wrote:

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I was interested so I went down to the shop and took a 12" long X 10" wide piece of 13/16" soft maple. I ripped it in half and jointed the dges. I used Lee Valley glue and rubbed the two edges together to make sure that I had a joint that was evenly coated. I took 3 pipe clamps and used a pipe wrench on the handles. The clamps left very nice depressions in the outside of the boards.
I let the glue cure overnight and put the piece in my vise. I used a ribber mallet and beat the board until it finally broke. It did not break along the glue joint. One sample does not prove the issue but I was not able to produce a starved glue joint even with 1 clamp every 5 inches or so (1 clamp 1" in from each and and one clamp in the middle).
A more scientific experiment would involve using a hydraulic press on small (1" X 1") samples.
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Soft maple is more porous that other woods. Hardwoods with little or no surface texture don't glue as well as woods like pine and mahogany. Also, 1 inch samples are not a great test because the short length of straight grain doesn't offer the board as much support and it will be more likely to split along the grain lines. WE would occasionally test glue strength by gluing up 3 or 4 strips into a top. The strips were 3 or 4 inches wide and 12 to 24 inches long. We then would put a strip at each edge raising it up off the bench and hit the center of the board until it split. Sometimes the glue joints failed if it was too cold in the shop when we glued it up. There are a lot of variables to an objective test. max

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The starved glue joint is a myth. The important part of the glue is the part that soaks into the wood. I suppose if you could squeeze any excess glue out before it had a chance to soak in a significant amount maybe you could "starve" the joint. At a normal working pace, plenty of glue gets into the wood and the thicker the layer between the two pieces of wood, the weaker the joint. IMHO.
bob g.
David Chamberlain wrote:

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<snip>

<snip>
From all the research that I have read, the strength of the joint is not directly proportional to the clamp pressure applied. Certainly using a pipe wrench to tighten a clamp is overkill.
Normal hand pressure (or even less) is probably best if a nice thin coat of glue is applied to both surfaces.
OTOH, I have not mastered this either and learn with every new project.
Lou
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On Sun, 7 Nov 2004 16:41:21 -0500, "David Chamberlain"

Attached is the text of message from Franklin - makers of titebond. This msg was originally posted to this forum and am sorry i can't credit the original poster.
Response from Frnklain/Titebond rep re:Calmping Pressure
After our discussion here, I wrote to technical support at Titebond regarding our discussion of clamp pressure. I got a next day reply from a very knowledgeable and helpful gentleman, Mr. Zimmerman. I'm posting it here.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ I am writing in response to your question about clamp pressure. First, your calculation and understanding is correct. If you wanted to produce 200 psi over an area 12" x 12", you would need 28,800 pounds of force. On the other hand, it is not clear whether you often, or ever, fell short of the actual, required clamp pressure.
The actual required clamp pressure for any bond involving a wood glue is a combination of the small amount of pressure required to squeeze the glue into a thin, consistent layer, and the pressure necessary the compensate for any distortion or lack of fit in the wood stock being used. That means when the surfaces of the pieces being joined are true, and there is no gap between the pieces when they are dry fit, very little pressure is required. If, however, the same assembly is being made using pieces which are bowed, twisted or ill-fitted, the required pressure is much greater, and is largely the pressure required to straighten the wood and pull it into position. Thus, the actual required pressure for a bond also reflects the thickness, or fight, of the wood involved, with much more pressure obviously required to straighten a very thick piece of maple or oak than to straighten a thinner piece of the same species.
In many applications, then, pressure, serves to compensate for some lack of diligence in wood preparation. That being the case, good wood preparation lessens the need for, or dependence on, pressure. In the case of our literature, the high suggested pressures reflect the fact that those individuals being addressed include those who, at least on occasion, are trying to bond thick, poorly fitted pieces of wood, and for those readers, the high, suggested values are, indeed, necessary.
Finally, because the bond strength produced in a joint is the result of the entanglement of the glue particles which have been drawn into the pores and anchored to the wood on the two sides of the joint, there is rarely any concern for applying so much pressure that the glue is all squeezed out.
In fact, the bond strength achieved increases as the bondline or layer of glue becomes thinner. Given that fact, there are only two situations in which high pressures may be counterproductive. First, there is always a concern that the pores of wood at the bonding surfaces not be crushed, and that is the reason that our listed pressures are lower for the softer woods. The second situation deals with bonds involving end grain or other open grain. There the concern is that the open grain is prone to suck up a large amount of glue and, if that thirst has not been quenched before clamping, that excessive absorption of glue may result in a starved, and weak joint. Because most bonds involve face or edge grain which is relatively straight, that particular risk is rarely a concern. I hope this response is helpful, and ask that you feel free to write again or to call me at 1-800-###-#### if I can be of any further assistance.
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What a pleasant way to say "Our glue will hold with little or no clamping pressure if you guys would get your shit together and make tight joints with straight wood... lol
Thanks for posting that... it is good info and a reminder to not blame the glue for my poor workmanship and to be more diligent in learning good joinery..
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mac davis wrote:

Actually, what he said was quite different and positive not negative, "Our glue will hold if you bring the joints together, either with perfect jointing which then requires little pressure or with imperfect jointing which requires whatever pressure is needed to squeeze glue out along the entire length of the joint."
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