What is a Biscuit Joiner?

A biscuit joiner, sometimes called a biscuit jointer, is a woodworking power tool used in joining pieces of wood together. A biscuit joiner is ideal for joining wood together at corners as well as for joining wood aligned on the sides such as for a table top. A biscuit joiner creates professional looking edges on shelves, picture frames, and cabinets, as well as many other household items and craft projects.

A biscuit joiner is used to cut slots into the wood to be joined and then a biscuit is inserted between the glue-coated slots to create a secure joint. Biscuits for joiners are oval wood shapes that fit into the slots and help to hold the biscuited joints together, with the help of woodworking glue and clamps.

Beech wood is commonly used for biscuits because of its strength. Pressed beech wood laminate biscuits are designed to expand when they are exposed to glue. This way, the biscuits are placed into the slots cut by a biscuit joiner a little loose and then swell to fit the glue-covered slots to ensure a strong professional joint.

Biscuits should be stored in a plastic zip lock bag or covered plastic container when not in immediate use as they absorb moisture from the air and swell. Even the tiniest bit of moisture or dampness causes woodworking biscuits to expand and make them too tight of a fit for the slots made by a biscuit joiner. Biscuits should have some 'wiggle room' when they are first put into the slots. Compressing expanded biscuits in a vise or using sandpaper on them just before placing them into the slots cut by a biscuit joiner may help.

A biscuit joiner is also called a plate joiner. Biscuit joiner hardware produces slots shaped in half circles. A knob sets the angle required, often 45 or 90 degrees, while an adjustable piece called the fence guides the height and depth requirements. The biscuit joiner's fence keeps the cut parallel to the edge of the work. A good quality fence allows for accurate results with a biscuit joiner, but a poor quality fence can cause errors in alignment.

Although biscuits can be cut with a router, damage to the work is likely unless the router is mounted in a table. Moreover, plunge depths and cutter bearings may need changing more frequently when a router rather than a biscuit joiner is used, as router cutters are smaller than biscuit joiner cutters. Biscuit joiner cutters usually need replacing after every few sharpenings as the thickness of the cutter lessens with each sharpening.