LumberJocks

Reply by AESamuel

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Posted on Glue up pressure and number of clamps?????

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AESamuel

93 posts in 1616 days


#1 posted 01-18-2018 07:36 PM

I think the obsession with clamping force is related to the obsession with lots of glue…more is always better, right?

Watching videos on YouTube of some people’s glue up, 90% or more of the glue loaded up ends up squeezed right out of the joint. Look at the glue line on an edge jointed board, it’s almost invisible because the glue isn’t a filler(generally) it’s a bonder.
Glue is the strongest part of a joint, especially if there is no mechanical strength at play so if you apply X psi with the clamps and squeeze all the glue out of it you are severely weakening the joint. Another thing to note is that if you use a ton of glue it is going to continue to seep out of the joint a while after you have clamped up so you’re going to have to come back in twenty minutes and re-tighten them again.

So it’s a balance, not too much, not too little. Think about some of the techniques people used to use for joining boards before metal clamps were readily available. Wooden cam clamps, timber dogs and even twisted string loops! I’d wager the majority of those joints are still together today…

In regards to your scenario, assuming the mating surfaces are fitting well then I would be more concerned with even clamping pressure rather than amount of pressure. Three clamps “hand tight” or maybe four if I was unsure about the mating surfaces and I would be more than happy!


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