I created a post here a few weeks back about a laminated neck I wanted to make out of sapele and white oak. I ended up ruining all that lovely wood. I made mistakes cutting the scarf joints, but even more problematic was that the laminations did not seem to really hold together well. I picked up some of the scraps after I had wrecked all the wood screwing up the scarf joints, and I could snap the wood at the glue joints with my bare hands. I mean, I really had to grunt and strain to do it, but they did snap along the glue line.
When I glued up the three pieces of wood, I made a [ Sapele | White Oak | Sapele ] sandwich, and I used Tight Bond 2. I had 3/4" thick white oak boards that I used as clamping cauls to distribute the clamping pressure, and I had 4 bar clamps underneath the 5 boards (2x white oak cauls, plus the S|WO|S sandwich), and I had 6 super heavy duty C-clamps, plus 1 nice F-clamp clamping from the other direction. I even broke out my goofy Kregg jig's vice-style clamp that you screw down and then squeeze hard until it locks clamped.
So with 12 clamps and hardwood cauls, I cannot imagine that my problem was that I didn't have enough clamps. I also absolutely slathered the wood on both sides with glue. I had a plastic sheet down to catch all the drips, so I just went nuts with the glue. I used a paint stirrer to spread it all out evenly and over the edges. There was not a single micron of wood that did not have glue liberally added. When I clamped it all up though... I think I may have over-tightened the clamps. I started with the whole assembly resting on the pipes of the pipe clamps, and slowly tightened the pipe clamps just until each one was touching the wood; no pressure. Then I added the c-clamps from above, aiming for the middle of the boards, and still just screwed them down until they were just holding, and not falling over. Then I went back to the pipe clamps, and gave each one a half turn, starting from the inner-two, and then the outer two. Then I did the same thing with the C-clamps, and just kept doing that until, well... until I couldn't turn the handle anymore. I didn't 100% Hulk-out and really break out the crowbar, but I did turn those clamps until the wood sandwich have compressed the oak cauls so that when I took them off, you could feel a distinct ledge where the oak had been compressed.
So... I've heard before, that you can over-squeeze a glue-up, and end up starving the joint of glue by literally squeezing it all out. But then I've also heard from several sources that it is total B.S. and that PVA glue is so strong, that all you'd need is a 1 micron-thick film of it to create a joint that is stronger than the wood around it. And that even a 10 ton press could not completely squeeze it all out.
So... keeping in mind that these are all just YouTube videos that I've been using for reference, can any of you guys speak to how to dial in the "right amount" of clamping pressure?
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