That article is nonsense (or an error). Compression strength for wood across the grain is approximately 4MPa (600psi) for pine and 7MPa (1000psi) for oak. Clamping pressure they recommend is around crushing point for wood.
Further from the article: "But joints clamped at the recommended levels will be quite strong enough, with the glueline being stronger than the wood itself". The glueline will be stronger than wood itself even at 1/10 of the pressure they recommend. How did they determine "optimal" anyway?

 

WOW! And I thought I had enough clamps! Hey honey where is that credit card I'm going to Rockler!

 

This question has come up before on this forum. The consensus then was that the article was simply wrong.

If I were gluing up some maple that was 24" long, I would probably use 3-4 F-style clamps. In my opinion, that number of clamps just feels right.

 

Thanks for the feedback. I thought it was goofy myself.

 

Clamps ever 6" is more than ample in my opinion.

 

In my experience with gluing (which is on the high end for gluing simple edge and face joints) I've tried all different kinds of "clamping force" techniques to see the different outcomes. I've never had a glue joint failure with any. What I can say is that the most important aspect to getting a quality joint is to apply the clamps in the right position as FWW helped describe here. This, to me, is the key of laminating properly….

 

IMHO if you clamp with that much pressure I would think you would squeeze all the glue out thus starving the joint. I only tighten clamps enough so I get a little bead of squeeze out and call it good. Never had a glue joint come apart or fail.

 

I believe in the very next issue they corrected that article saying what several of you opined; the preassure needed as given was nonsensense, and the clamp distribution was preferred. However,, Childress and DLCW have it right. Overtightening will starve the joint, and proper positionog of clamps is the critical factor. IN other words, they wuz right and FWW mostkly wrong, except where they were partly right. I'm going to bed now.

Steve