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

  1. #16
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    Well the article did cause me to tighten my clamps a bit more than usual and add a few more this morning. This was for an epoxy glue-up that he didnt use, but I'll keep my fingers crossed. So far I've still got a fairly normal bead of squeezeout between all the joints so I dont think I'm starving the joints.
    Use the fence Luke

  2. #17
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    When I do segmented turnings, I just rub the 2 pieces together to get a good coverage and the only squeeze out is from pressure I apply myself. My glue joints come out very tight and have never failed to date. I truly think there needs to be a thin film of glue in the joint for maximum adhesion. I would guess around 250 to 300lbs of pressure would be adequate. Oh well, what ever works for whom ever I guess.
    What you listen to is your business....what you hear is ours.

  3. It's been my experience that Titebond tends to be pretty squeeze out resistant and I have on several occasions gotten somewhat carried away with my clamping.

    However, epoxy can be subject to glue starvation rather readily. I did a maple panel last winter (over clamped it) and in the morning it came apart in my hands.

  4. #19
    Keep in mind that magazines have to fill their covers with articles every month. Eventually there isn't much more to be said on a specific topic - after all, the stuff in wood working magazines is rarely news. So they have to keep giving different spins on the same old stuff.

    There are lots of ways to do a lot of things - briefly looking at posts in this forum proves that. So I take what I read as potentially interesting - not as potentially the law of the land.

  5. #20
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    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.

  6. #21
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    Quote Originally Posted by Doug Shepard View Post
    Well the article did cause me to tighten my clamps a bit more than usual and add a few more this morning. This was for an epoxy glue-up that he didnt use, but I'll keep my fingers crossed. So far I've still got a fairly normal bead of squeezeout between all the joints so I dont think I'm starving the joints.
    Be careful, that article has not relation to epoxy adhesives. Epoxy requires a certain amount of film thickness to get fully adhesion and strength. Epoxy should not be clamped any more than necessary to keep the parts together. Clamp too tightly and you will starve the joint and it will be weak.

    The article deals specifically with PVA adhesions as the author makes clear. While most other waterbased adhesives will be close to the same as far as clamp pressure is concerned, each will be somewhat different.
    Howie.........

  7. #22
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    Yea, I read it too and thought it was crazy. This would mean that all the woodworking I've been doing over the past 30+ years is all wrong AS WELL AS meaning that this kitchen table I'm doing would have required over TEN TONS of clamping pressure!!!!!

    I'll just stick with what I know is working for me and let them be all scientific and stuff in the magazine prints.
    Thanks & Happy Wood Chips,
    Dennis -
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  8. #23
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    Fw`s Article On Glue-ups Or Friction

    If they would put a little more Fine Wood Working in the magazines and a little less b.s. it would suit me fine. Next week they will have a clamp with a torque wrench on the end of it they are testing. Its more like a consumers report than a wood working magazine. Barry Bruner

  9. #24
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    Quote Originally Posted by Barry Bruner View Post
    If they would put a little more Fine Wood Working in the magazines and a little less b.s. it would suit me fine. Next week they will have a clamp with a torque wrench on the end of it they are testing. Its more like a consumers report than a wood working magazine. Barry Bruner
    I agree. The change in the magazine over the past few years has been sort of like going for the lowest common denominator. I remember when it dealt with rather high end furniture making and such as that. It does now seem to be more about tool testing and projects for the less talented woodworkers among us. That's fine I guess, but they're starting to bore me, frankly. Taunton Press has to do what they have to do to keep the most readers so they can sell advertising, I know, but...
    Visit Peercon.com

  10. #25
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    I am of two minds on the topic

    As an engineer I was interested in the article and actually disappointed that it was so brief. What I would have liked to have seen would have been a graph of resulting joint strength versus clamping pressure. I will bet the curve has 3 distinct regions (too little, approximately right and too much) I would guess there is an ascending ramp of strength versus pressure on the too little pressure region , then a flatish portion where the wood is breaking next to the glue (over a range of clamping pressure) and then finally a descending ramp when you get into the starved joint region from too much pressure.

    My guess is that the reason so many people are shocked and express either concern about previous glued panels or feel like knocking the article is that all the gluing methods they have been using are working and they know it. I would not be surprised if there is a pretty broad pressure region where joints achieve at least 80% of maximum strength (from the author's quoted pressure values). Recall from FWW #192 that the loose bridle joints (no wood contact with a 1/64" gap) for PVA were at least 80% as strong as the tight fitting joints.


    Everybody complains about FWW. There is always something I like in each issue and usually a lot I can do without, but of all the magazines I have ever read, they are the only ones I keep and reread. I myself most like the articles about furniture and about wood itself. Garrett Hack wrote an article recently about 5 underused North American woods, that was a really cool article.
    Last edited by Jeff Booth; 10-06-2007 at 11:09 PM. Reason: typo

  11. #26
    Quote Originally Posted by David Weaver View Post
    The PSI at the joint shouldn't reflect the amount of surface area of the clamps - if they're clamping with 500 pounds of pressure, that's 500 pounds. I sure would worry about the wood fibers on a cherry panel using one of those iron bar clamps with 1500 psi of pressure. I'm assuming that you're saying that you can get a lot more clamping pressure at the same psi at the jaws of the clamp if you use the bessey style clamps.
    Surface area definetely IS part of pressure. In college physics we calculated the pressure of an elephant's foot compared to an average woman's high heel. Guess which pressure was higher!
    Last edited by Jim Becker; 10-06-2007 at 10:43 PM. Reason: Fixed quote tagging

  12. #27
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    How about Vacuum Bagging?

    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.
    Tom Veatch
    Wichita, KS
    USA

  13. #28
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    I would hazard a guess that veneer to substrate joint doesn't require nearly the strength that an edge joint in a panel needs. As someone else pointed out, the author was making the claim that in order to get MAXIMUM adhesion (even though it may not be necessary), those clamping pressures were recommended. He didn't say that anything less would lead to immediatle self distruction of the piece.

    I wonder if clamping pressure is at all correlated with glue creep?

    Dan
    Eternity is an awfully long time, especially toward the end.

    -Woody Allen-

    Critiques on works posted are always welcome

  14. #29
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    Quote Originally Posted by Paul Hendrickson View Post
    Surface area definetely IS part of pressure. In college physics we calculated the pressure of an elephant's foot compared to an average woman's high heel. Guess which pressure was higher!
    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.
    Last edited by Kent Fitzgerald; 10-07-2007 at 1:17 PM.

  15. #30
    Quote Originally Posted by Paul Hendrickson View Post
    Surface area definetely IS part of pressure. In college physics we calculated the pressure of an elephant's foot compared to an average woman's high heel. Guess which pressure was higher!
    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.

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