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Thread: FWW's article on Glue-Ups Fact or Fiction?

  1. #31
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    >> I guess you can forget about vacuum bagging veneer work since the most a vacuum bag can give you is only about 1/100 of what's needed.

    Well, as you said, you have not read the article and are relying of second hand info. The article dealt with a rather narrow type of joint. Namely, edge to edge or other joints where maximum strength was a criteria. There is not much strength needed for veneering. Any adhesive that keeps the veneer from falling off is sufficient. But, vacuum bagging would not be the choice for structural joints.

    As to creep, clamping pressure does have some effect. The more closely you can bring to wood surfaces together, the less adhesive there is to stretch.
    Howie.........

  2. #32
    If it ain't broke, then don't fix it.

  3. #33
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    Well, from what I have gathered by my experience and what I have been reading, not many people are glueing up so that they get 100 % maximum strength. Now, my question is what percentage is good enough? 80%...70% or even 50% ?

    Maybe 50% is all we really need. Maybe the fact that were getting 70-90% is really good enough and we do not have anything to worry about.
    Thats my 2 cents and I'm sticking by it.
    Gary

  4. #34
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    Quote Originally Posted by Steve Schoene View Post
    The manufacturers have been calling for similar clamp pressures for a long time, and it's certainly not in their interests to tell you to do something that weakens the bond. So why haven't all of Norm's, "don't squeeze out all the glue" joints not failed? Because in most cases edge joints have enough strength to perform satisfactorily even if they don't have maximum strength. But since clamping more firmly has such little cost it doesn't pay not to go for stronger.

    But the story that also needs telling is how to get a joint suitably prepared for gluing. Again, lots of less than perfectly fitted joints will hold up OK because of the "safety factor" built in, but to get a joint where there is NO visible glue line is a different question. By no line I mean that you can only tell the wood is joined when several grain lines all stop at the same plane under close inspection. That's not what you get directly off the saw, or with a quick pass on the jointer except in the rarest of cases.
    Norm often reinforces his glue joints with nails. He also does a lot of plywood joints. Does it not make sense that the glue manufacturers, Bruce Hoadley, Dept of Forestry Wood Handbook all have the same recommendations of pressure. Or is it all one giant conspiracy?

    Vijay

  5. #35
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    Quote Originally Posted by Tom Veatch View Post
    Haven't read the article, but hearsay from another source indicated a need for about 1200 PSI clamping pressure for flatsawn sugar maple. If that's correct, and is any indication of the general need, I guess you can forget about vacuum bagging veneer work since the most a vacuum bag can give you is only about 1/100 of what's needed.

    Let's see now. At 1200 PSI, a 1 square foot veneered panel would require a 86.4 ton press.

    Obviously something's not right with this picture.
    The article only talked about edge gluing boards, not veneering. The article is worth reading.

    Vijay

  6. #36
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    Quote Originally Posted by Steve Schoene View Post
    The manufacturers have been calling for similar clamp pressures for a long time, and it's certainly not in their interests to tell you to do something that weakens the bond.
    Titebond recommends 'enough pressure to bring the joints tightly together generally 175-250psi for hardwoods' vs the 600-1200psi recommended by the author.

    I was very disappointed with the article. The author Roman Rabiej has a good CV and appears to have done research in this area. It was unfortunate he didn't feel the need to share any of it beyond some unrealistic recommendations.

    It would be impossible for any hobbyists and 90% of professional woodworkers to glue up a 2" thick maple workbench using his recommendations.

    Greg

  7. #37
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    Yes, it makes a lot of sense. That's how I was taught, and it's a very good practice. Yeah, you can get boards to stay together without being so precise, but I'll reiterate that you can't make the glue line disappear so thoroughly.

  8. #38
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    Pressure is "force per unit area" or Newton per square meter or Pound per square inch (psi).

    So 1 lb over 1 square inch is 1 psi. 1 lb over 0.1 square inch is 10 psi. 1 lb over 10 square inch is 0.1 psi.

    Cheers
    Wood: a fickle medium....

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  9. #39
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    I wil ltry ot say this right, hopefully you all get my meaning anyway.

    Concerning the Gov't lab tests.

    When they do a test it is only to confirm what the manufacturer tells them.. Sort of just a confirmation. SO it will always be likely that the test lab will agree with the manufacturer concerning things like. well clamp presres for glue ups.

    If they find something below the range it gets reported and before it gets recorded, the manufacturer wil gwet an oportunity to correct the situation. If they find it is higher/better, in this case, that does not get reported.
    A cookie in each hand is a balanced diet.

    My next tool will be the last tool I ever need!

  10. #40
    Quote Originally Posted by Kent Fitzgerald View Post
    David's point is correct. He didn't say that area wasn't important, he said that the area of the glue joint (not the clamp face) is what matters for determining gluing pressure.
    I was referencing the difference in a Bessey vs. Quick Clamp from the article, which is what he was mentioning as well. There is no way a Quick Clamp is stronger than a Bessey, until you factor in the much smaller area of the Quick Clamp. Translation: Quick Clamp may have higher psi, but factor in larger surface area of Bessey, and it becomes much more useful.

  11. #41
    Quote Originally Posted by David Weaver View Post
    If you give me the surface area and weight or mass of both, I'll give you an answer, but based on the context, I'm going to guess the woman.

    Speaking of, we got one of those new bamboo floors in our office at work - one of the new smart looking laminated things, and guess what it can't handle? High heels - it can't handle hard high heels - they dent it. That's sort of along the same lines as what we're talking about.
    It was definitely the woman's heel. And to relate it to this discussion, the woman's heel would dent the bamboo, whereas an elephant's foot would not dent the bamboo but would be more likely to bust up the concrete underneath.

  12. #42
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    Quote Originally Posted by Anchor Sarslow View Post
    Concerning the Gov't lab tests.

    When they do a test it is only to confirm what the manufacturer tells them.. Sort of just a confirmation. SO it will always be likely that the test lab will agree with the manufacturer concerning things like. well clamp presres for glue ups.
    That's not the case here. The Forest Products Laboratory is a function of the USDA who's mission is to develop and publicize the best practises in the wood uses. They publish this info in a document titled "Wood Handbook" which can be downloaded or viewed here: http://www.fpl.fs.fed.us/documnts/fp.../fplgtr113.htm

    Their tests are not intended to varify the performance of brands of adhesive. Rather they are concerned with how strong a joint needs to be.
    Howie.........

  13. #43
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    I read the article and assumed it was correct, given the author's credentials, but could been written more clearly. The required pressures he gave were for what he called "optimum" glue joints, which I had to assume must be much stronger than the wood being glued. If a joint is at all stronger than the wood itself, in my opinion it's strong enough.

    So the article would have been more useful if he had expounded on the difference between"optimum" and "adequate" glue joint strength. If I did the arithmetic correctly, it wouldn't be possible, using his numbers, to get enough parallel jaw clamps on a panel to achieve the "optimum" pressure. (I admit I did the arithmetic on a napkin between bites of lunch and don't have the article handy.)

    On the subject of the force exerted by the different types of clamps, it was given as force in pounds, not pressure in pounds per square inch. If you divide the pounds of force applied by a clamp by the area in square inches that the clamp is acting on, you get the pressure in pounds per square inch.

  14. #44
    Quote Originally Posted by Carl Eyman View Post
    Did anyone else have fear struck in their heart by FWW's article on how to glue up a panel. [snip]

    What do the rest of you think?

    The author's credentials are impressive; so I feel uncomfortable in questioning his conclusions. But . . .
    I'll simply copy what I posted on the wreck (usenet, rec.woodworking) to the question asked there on the subject:

    I moved on the instant I saw the glue up with the QuickGrips on it. He
    asserts you can get greater pressure with them than K-Bodies? Please.

    I bought my first QuickGrips probably 20 years ago. It took me all of
    about five minutes to figure out they were possibly okay for some
    tasks, but you couldn't depend on them staying clamped and they
    definitely couldn't be clamped really hard. Those first ones were also
    my last ones.

  15. #45
    Quote Originally Posted by Vijay Kumar View Post
    The article only talked about edge gluing boards, not veneering. The article is worth reading.

    Vijay
    Wasn't worth reading. As a matter of fact the entire issue was worthless. Why the article on routers for beginners?
    FWW wasn't designed for beginners.

    Let's just say another goofy engineer who has more degrees than sense wrote that article.

    The only thing that I have read is that Franklin (Titebond) recommends that your joints don't have more than a .003 gap. Maybe that goofy engineer can't make straight edges so he has to squeeze the sh#@ out of them to get them to those specs.

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