A biscuit joint is a type of woodworking joint developed in the 1950s. In a biscuit joint, an oval-shaped piece of wood known as a biscuit is inserted into slots in the two pieces of wood to be connected. Glue on the biscuit causes it to expand, creating a snug fit and a very clean joint. The mechanics of a biscuit joint are totally hidden, making this technique popular for applications where woodworkers do not want people to be able to see the joint.
This style of woodworking joint is an example of a butt joint. Butt joints are made by butting two pieces of wood together, and they tend to be weak without reinforcement. The biscuit and glue combination makes excellent reinforcement, ensuring that the joint will be very strong. In fact, the joint can be stronger than the wood itself, and biscuit joints rarely fail when they are made properly.
Biscuits can be made from solid wood or laminated wood products. Laminated woods are sometimes preferred, because the moisture of the glue will puff up the layers in the biscuit, ensuring that it enlarges. Beechwood is a popular choice because it is very strong, although other woods can be used as well, and biscuits come in standardized sizes: #0, #10, and #20. The larger the number, the bigger the biscuit, with the goal being to use the biggest biscuit possible for extra strength.
Slots for a biscuit joint can be cut with a variety of woodworking tools, but many people prefer to use a biscuit joiner, also known as a plate joiner. Biscuit joiners are specifically designed to cut the half-rounds used to make biscuit joints, and they are very easy to use. Users simply set the size and angle desired, and make a cut in the intended locations. The cuts do not have to match perfectly, as there is a little bit of wiggle room in a biscuit joint.
Woodworkers usually learn about a range of possible joints they can use during their woodworking education. They also practice extensively so that they can get a feel for how each type of joint looks and behaves, which allows them to select the best joint for the job. People working on woodworking projects at home who have not had professional training might want to consider a weekend course so that they can get some experience and mentoring which will radically improve their woodworking projects. Biscuit joints are popular because they are strong and easy to make, but there are other options as well.