Avoiding Gaps in Your Glue Up

Article - April 23, 2008

This week’s question comes from Mike. He writes:

My most recent project as I’ve mentioned to you before is a baby crib for our first child. This crib will later convert to a day bed and then a full size bed. Therefore there are several legs that must be built first, 6 in total. These legs are built up of 3 pieces of 3/4″ maple laminated together. The center piece is planed slightly thinner to match the thickness of 3/4″ maple ply for the rails that will be mortised into the legs. Once I began to glue the boards together I realized I have some difficulty when it comes to clamping, more specifically knowing how to clamp properly.

I recently purchased some of Rockler’s F-style clamps. I love them and started with them however I quickly realized that they were probably not the right clamps to use for this application. I then grabbed some of my hand screw wood clamps. They seemed to give me a better spread across the boards which are 2 3/4″ wide. I supplemented with the f-style clamps using wood blocks to spread the clamping pressure evenly I do not own any small parallel jaw clamps or I would have used them for this job. What I ended up with was some of the legs went together well with no gaps in my glue joints while others has small gaps in the glue joints the full length of the legs that will have to be filled. How can I avoid this in the future? I’m not concerned that they will come apart because there will be some fasteners that go through the legs to attach the railings, but I would like to have tight glue joints when laminating several boards together so I don’t have to do so much gap filling before I go to finishing.

And here was my reply:
Hey Mike. Excellent question. Using “less than optimal” clamps is something many of use have to deal with. And there really is no big secret. It just comes down to lots of clamps and lots of pressure. I would recommend using cauls that are at least as long as the leg is wide. Then, I would use the F-style clamps to clamp down over the cauls. And since one clamp in the center of the caul may still not apply enough pressure at the edges of the leg, I would recommend putting two F-style clamps at the ends of the neighboring caul. So in effect you will alternate: one centered, two on the edges, one centered, two on the edges, etc… Do this across the leg every 4-5 inches (the closer the better), and you should have enough pressure. From your description, it really sounds like you had enough pressure at the center of the leg, but not at the edges. Of course this means you need a lot of clamps! But as they say, you can never have too many. And kust so you know, the way I do this: I use the parallel clamps and alternate the sides they clamp from. Then I actually reinforce the clamping with F-style clamps in between the parallels. Good luck.

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