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

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  1. #1
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    FWW's article on Glue-Ups Fact or Fiction?

    Did anyone else have fear struck in their heart by FWW's article on how to glue up a panel. I've obviously been doing it all wrong for 40 years. I expect the next time I look at a panel I've done I'll be watching it come apart as I watch. I'm not arguing with the author, but I'm sure I've been using a lot less clamps and a lot less pressure than he recommends. Yet I look at panels every day and can't think of one that has failed.

    What do the rest of you think?

    The author's credentials are impressive; so I feel uncomfortable in questioning his conclusions. But . . .
    18th century nut --- Carl

  2. #2
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    Slightly OT, but what struck me was the fact that a Quick-Grip clamp was rated at 470lb, whereas a parallel jaw clamp was rated at 370lb.

  3. #3
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    Me Too

    Quote Originally Posted by Alex Berkovsky View Post
    Slightly OT, but what struck me was the fact that a Quick-Grip clamp was rated at 470lb, whereas a parallel jaw clamp was rated at 370lb.
    I have to doubt him on this or he had a gorilla using the Quick Grip. When I've tried to bring a tight joint together with the Quick grip and failed a parallel jaw has worked.
    18th century nut --- Carl

  4. #4
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    Exclamation

    Quote Originally Posted by Alex Berkovsky View Post
    Slightly OT, but what struck me was the fact that a Quick-Grip clamp was rated at 470lb, whereas a parallel jaw clamp was rated at 370lb.
    Me too. That's really all I wanted to say, but the forum software apparently needed a longer message for some reason, so I'm writing more here
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  5. #5
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    Quote Originally Posted by Alex Berkovsky View Post
    Slightly OT, but what struck me was the fact that a Quick-Grip clamp was rated at 470lb, whereas a parallel jaw clamp was rated at 370lb.
    I said the exact same thing to my BIL last night. I feel that there needs to be some glue left in the joint to, well, glue it together. As far as those clamping preasures go, that can't be correct.
    What you listen to is your business....what you hear is ours.

  6. #6
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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

  7. #7
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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.........

  8. #8
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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,
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  9. #9
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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

  10. #10
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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...
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  11. #11
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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

  12. #12
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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.

  13. #13
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    I have never found that credentials are written in stone when it comes to things that I have experienced and work for me, but I am not beyond learning from someone else's expertise. If it makes sense maybe the author has a good point. If not, why change now?
    David B

  14. #14
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    Before we get to far afield, let me point out that the two manufacturers of PVA adhesive (Franklin and Borden) specify the clamp pressure quoted by the author. In addition, the USDA, Wood Products Laboratory in their Wood Handbook specify the same clamping pressure.

    Also, a properly prepared joint will hold together with less pressure. But, for maximum strength and minimal glue line, the higher pressure is required.
    Howie.........

  15. #15
    He's probably correct about clamping pressure needed, but I find the ranking of the clamps kind of hard to believe.

    You can bend bessey clamps - they have to be putting out more than 300 pounds of pressure when the bar is bending.

    It seems better to spend the time making the joints right so you don't have to clamp the shizz out of them.

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