Can Glue Joints Be Clamped Too Tight?

Clamping Clamps Glue


Many people are worried about over-clamping. I say that’s absolutely not a concern. Here’s why:

Consider this. I have a cutting board that is 12” x 18” and 2” thick. It consists of many boards glued together to make the whole thing

Let’s take two of those interior boards. They are 2” tall by 18” long.  And I have to glue them together.

2x18 = 36 square inches of glue surface.

It’s a hardwood. So Titebond says I can use 250 pounds per square inch in clamping force.

36 square inches x 250 pounds per square inch = 9000 pounds of clamping force recommended.

Who would have thought that two little boards should be clamped together with 9000 pounds of force??!

Well, the scientists & engineers at Franklin Adhesives (makers of Titebond), who have been studying the chemical & physical properties of PVAs & have been extensively researching how to achieve the very best bond for the last three quarters of a century think that it’s necessary.

So I generally defer to them on this aspect. My take is that if a manufacturer of a product employs research scientists that determine the best way to use their product, then that truly is the best way.

Now let’s get practical. This glue up is only 18” long. How do I get 9000 pounds of force on it? 

It looks like I can get 7-8  pipe clamps on it. But the truth is, that would just barely fit. 

In all likelihood, we aren’t going to try clamping to such extremes. But I did this exercise to prove a point. It’s exceedingly hard to over-clamp. Mostly because we’d have to fill every square inch with clamps.

So my advice is to do this:

Use as many clamps as will comfortably fit. And secure them tightly. Almost certainly you will get a great joint. (Probably not the strongest possible, but that’s ok) And, you will have no fear of over-clamping.

If you are curious as to the science behind why a very tightly clamped joint is so strong, I’ll tell you. PVA adhesives have great adhesive strength (meaning they stick very strongly to other things), but they have a very low cohesive strength (meaning they stick very poorly to themselves).

The reason high pressure is great is that it forces the bond to have a very thin layer of adhesive inside. So that virtually all of the strength of the joint is adhesive strength.  If the joint has a thick layer of glue inside, then we are also relying on cohesive strength. Or the ability of the glue to stick to itself. (Which we know is poor).

This is also why PVA glues are considered poor at gap filling. Inside of a gap is a large amount of glue that not only must stick to the wood on either side of the gap, but it must stick to itself over a considerable thickness. Which it does poorly due to its low cohesive strength.

Epoxy, on the other hand, is a great gap filling glue. It has high adhesive AND high cohesive strength.


Titebond official recommendations:


Fine Woodworking article:

“Most woodworkers are underclamping their joints during glue up.”

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  • RYan Gratland on

    Thank you for taking the time to drop this knowledge in one easy to follow article. As a “glue master” recipient it’s awesome to factually understand the reasoning behind gluing and clamping methods. Thank you.

  • Richard Rosen on

    Unless I missed it I didn’t see any discussion about buckling of thinner boards and force superposition, i.e., the clampling force is not just perpendicular from the face of the clamp but spreads between clamps. In order to model this properly you’d have to consider the Young’s Modulus and Poisson’s Ratio of the assemblage of mating woods.

  • Esam Abudraa on

    Hi . King,

    I really enjoy & appreciate all your pointed out advise in your all youtube videos.

    Many thanks .
    Esam Abudraa.

  • Pete Wadner on

    Sir you are the first person showing how make something out of wood that does need the cost of very expensive tools. Also I was surprised that you did not glue up any joints. I liked that. Will watch more of you videos. Ill make the chairs I have just received the plans for thanks. Cheers Pete UK.

  • Tony May on

    Dear M. King, In 1988 I renovated a 200 y.o. house replacing the softwood with hardwood doors and windows. A local firm did this custom job. I was astounded to find that they were using massive hydraulic presses to complete all the joints in the mahogany. The one thing that was tight was the frame inside the bricks and mortar aparture! Zero foam needed.

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