"Biscuit joiner" and "plate joiner" are different names for the same woodworking tool. The term "biscuit joiner" is more widely used in the United States. This tool cuts slots into two work pieces to join them; the slots accommodate a special football-shaped piece of wood, called a biscuit, that helps align the boards and strengthen the joint.
The Joiner Tool
A biscuit joiner is a saw with a 4-inch blade. The joiner operator, after lining up two boards in the manner in which they are to be joined, makes penciled layout lines across the two work surfaces. The line on the biscuit joiner matches up with the layout line where the cut is made. A biscuit joiner is adjustable in depth of cut and position of the fence. The depth-of-cut adjustment allows the use of several biscuit sizes, and the fence alignment adjusts to different joint angles.
Biscuits are made from beech wood shavings that have been compressed into an elongated oval shape. A biscuit brushed with wood glue expands rapidly to fill the slot created by the biscuit joiner. Biscuits are 0.148 inches thick but are available in three sizes of differing lengths and widths. The smallest biscuit, designated #0, measures 5/8 inch wide and 1 3/4 inches long. The largest biscuit, #20, is 1 inch wide and 2 3/8 inches long. The middle biscuit, #10, is 3/4 inch wide and 2 1/8 inch long.
A glue-covered biscuit is inserted into the slot that has been cut into both pieces of wood. After biscuit insertion, the two wood pieces are clamped together until the glue dries. The addition of biscuits makes weak joints, such as edge joints, much stronger. When a proper biscuit slot is cut into two pieces of wood to be joined, the biscuit helps to keep the boards positioned while still allowing a little room for any necessary adjustments.
Types of Joints Produced
Edge-to-edge glue-ups are the most common type of joint produced with biscuits. These are the type of joints used to create tabletops. Biscuits can also be used to strengthen: miter joints, such as those used in picture framing, butt joints, in which two boards are connected end to end; and T-joints, in which boards are arranged in a "T" formation. Biscuit joinery is also used in drawer construction and to attach moldings and edge bands.