How tight to clamp glue-ups?

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For the same reason, 2x4s or even 4x4s make better cauls for general glueups than thin scrap, because they widen the Vs at the glueline.
Even pressure is better than crushing pressure applied at few points. The glue is stronger than needed in most cases, but the finished joint will look neater.
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"blueman" wrote:

-------------------------------------------- Depends.
If you are using typical wood working glues like TiteBond II, then high clamping pressures are suggested by the manufacturer.
OTOH, if you are using quality epoxy, then only a minimum amount of clamping pressure is required to hold pieces in place while epoxy cures.
Different horses for different courses.
Lew
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Is higher clamping pressure bad for epoxy or just unnecessary?
What about for the various polyurethane glues?
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"blueman" wrote:

High clamoing pressure starves the joint of epoxy needed for a good joint.

I chose not to comment on that garbage other than to say it is overpriced and under peckered.
Lew
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On Wed, 10 Mar 2010 21:02:57 -0800, Lew Hodgett wrote:

Amen, brother!
--
Intelligence is an experiment that failed - G. B. Shaw

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On Wed, 10 Mar 2010 08:53:31 -0500, blueman wrote:

If you have tight fitting joints, hardly any pressure is needed. If not, no pressure is enough :-).
I've seen antique furniture with "rubbed" joint corner blocks that have lasted and lasted and ...
And don't overdo the glue. A thin even coat on each piece, thin enough that you can see the grain through the wet glue, is the best. But I've often gotten away with only coating one piece.
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Intelligence is an experiment that failed - G. B. Shaw

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...I use "rub blocks" frequently and have had opportunity to demo same for whatever reason...damn, they are VERY strong.
cg

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I agree that PVA glues will develop a strong hold and rubbing in a fit, like with corner blocks is totally valid. Hovere, if you are talking edge gluing a panel, I have sse the studies regarding how much clamp pressure and the outcomes are too little is less effective than enough and too much is hard to achieve. I really don't think Franklin (titebond) and others would clearly state clamping pressure is need for optimal strength if it wasn't proven science. Although they could be in some conspiracy with Bessy to make us all buy expensive but useless clamps.

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On Thu, 11 Mar 2010 06:48:55 -0800, Larry Jaques wrote:

More or less. I move the wood just 1/4" or so till I feel it start to grab. Then press it into the desired location - no clamps needed.
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Actually I can not remember the last time I actually put glue on both sides of the joint, my practice is one side only. Except when end grain is being glued.
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Unsolicited end-grain gluing info.
End-grain to any other grain, face, edge, end does not have any of the same great qualities of a typical glue joint. The fibers being perpendicular to the joint just don't allow for any long chain attachment. One technique is to "size" the joint (not sure if that is the right spelling for "size", I am speaking about the same concept as used with wallpaper). Anyway, add glue to the end grain and then let it mostly dry before putting the joint together. Then glue it again so the joint is gluing the glue on the end grain to the other piece. Haven't seen any science on this but have seen it recomended many times. Could be old wives tail.

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Unsolicited end-grain gluing info.
End-grain to any other grain, face, edge, end does not have any of the same great qualities of a typical glue joint. The fibers being perpendicular to the joint just don't allow for any long chain attachment. One technique is to "size" the joint (not sure if that is the right spelling for "size", I am speaking about the same concept as used with wallpaper). Anyway, add glue to the end grain and then let it mostly dry before putting the joint together. Then glue it again so the joint is gluing the glue on the end grain to the other piece. Haven't seen any science on this but have seen it recomended many times. Could be old wives tail.
That is exactly what I do. Coat the end grain and let it soak in and then reapply additional. Now if I am using pocket hole screws on the joint I simply apply one coat to the endgrain. Kreg claims glue is not necessary but IMHO it will not hurt.
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How the joint fits is of most importance with regard to strength. I apply just enough glue so that just a small amount oozes out. My clamps are "hand tight," but not "muscled tight." I dont believe a joint is starved of glue, some is absorbed into the wood fibers. Apply a thin coat of glue to both mating surfaces if using carpenter's yellow glue.
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