Expert: Jamie Yocono - 10/27/2011

Question
Hello

I'm working on a chair and I have drafted up a design where the seat of the chair is made up of multiple boards glued together and planed down. Much like the image attached. My worry, never having done this, is that it won't be strong enough. Is it strong enough to just use glue? If not, could you shed some light on the proper measures to take.

Much appreciated.

Answer
Hi Clay,

It is a widely held belief that when two boards are glued together, the glue joint is actually stronger than the wood itself. Glue manufacturers say that, magazine articles test it and have proven it true, and most woodworkers (myself included) have often done simple tests to see for themselves.

The way to test it? Glue to pieces of wood together, and when the glue is dry, try to break the wood apart. I've done this many times, and if the joint is properly glued, the wood will fracture before the glue line will separate.

Here is an interesting article I just found:  http://woodgears.ca/joint_strength/glue.html

With that said, there are still some measures that can ensure better results. Obviously, you want a very nice fit between the boards you're gluing. No gaps, if at all possible. Some woodworkers believe that a small gap toward the center is OK in a glue joint, but NEVER a gap toward the ends of a joint. That will eventually lead to separation over time.

The best gluing surface should have a little "tooth" to it. If you have a super sharp blade in your saw and the cut leaves no major teeth marks, that rough-sawn edge is perfect to glue up. The glue seems to work better with something that is a little rough, as opposed to something extremely smooth.

Finally - if it makes you feel better, you can add a dowel or a biscuit to your joint, but this is mostly for alignment issues, not for strength. Like I said - the joint is not going to come apart if glued properly. Make sure you use an adequate number of clamps - I like to put one close to each end, and then space the rest every 6-8" or so. You can never have too many clamps!

Good luck, I hope this helps.

Jamie in Vegas


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Jamie Yocono
Wood It Is! Custom Cabinetry
Las Vegas, NV
www.wooditis.com
My woodworking blog: www.wooditis.blogspot.com