In woodworking, there are three things that affect a wood joint: the adhesive, the wood, and the interface region (the area between the wood and the adhesive). You want to strive for a 100% wood failure. This means the adhesive is stronger than the wood itself.
When it comes time to start glueing your projects, the first part of the process includes deciding what type of adhesive you want to use. Make sure you understand assembly time, clamp time, and cure time for the adhesive you are considering.
Preparing the Wood Pieces
The next thing you want to prepare is the two or more pieces of wood that you will be gluing. The surfaces glued together need to be “dressed.” They should be smooth, knife-cut or sanded, and hold a tolerance of ±0.015 inch over 8 feet long. This tolerance can be achieved with a jointer or with straight-line rip saws that have a triple-chip blade. Sand the faces using a wide belt sander with 60-80 grit paper installed. Knife-cut surfaces are proven to have higher strength properties than sanded surfaces. These surfaces should be free from any dirt, chipped or torn grain, burn, or any machining irregularities. Dress the surface within 24 hours of applying the glue. This eliminates anything that could have developed on the surface of the wood.
Next, you can get ready for the glue-up. Get all or the clamps that you will need in the area you are working. Have a plan of how you want to glue your pieces together. You only get one chance to glue the pieces together.
Apply a thin, even layer of the glue. You want to apply enough glue that will hold the joint together. But too much glue isn’t always better. Applying too much glue can force pieces of wood away from each other. Plus, too much glue is a mess and is a waste of glue. You want to work quickly once you start applying the glue. This will prevent the glue from beginning to set up before you clamp the pieces together.
Lastly, apply a moderate amount of pressure to the joints with clamps. Some squeeze-out will come from the joint, but this is a good thing. It shows you that you applied enough glue and pressure. Pressure forces air out of the joint, squeezes the adhesive to a thin film, holds the assembly together while the glue sets, forces glue into the cells of the wood, and it brings the adhesive into molecular contact with the wood. Too much pressure can force too much glue into the wood cells and doesn’t leave enough glue to fill the bond line. This will result in a weaker joint. Let the glue completely cure before machining.