A biscuit joiner (a.k.a. plate joiner) is a good choice for light- to medium-duty joinery. It’s widely used to assemble panels in cabinet carcass construction, window casings, rail and stile doors, face frames, and furniture. Both corded and cordless models are available. The joiner looks similar to a portable angle grinder, but instead of a grinding wheel it spins a small 4″ saw blade with carbide-tipped teeth. On the front of the joiner is a movable and tiltable fence that registers against the workpiece. The saw blade is then plunged into the material to make a crescent-shaped groove. A matching groove is also cut in the opposing piece. Slots are generally made parallel to a board’s edge. Glue is applied to the grooves, an oval shaped “biscuit” (a.k.a. plate) is glued and inserted into the groove and the two pieces are clamped together. As the biscuit absorbs moisture, it expands slightly to fill the groove. Biscuits come in four sizes and are made of wood, metal or plastic. There are also interlocking biscuits that enable joints to be taken apart.
Price: $140 to $1,000
Power source: 110V (corded) or battery
Biscuit widths: FF (1-1/4″), #0 (1-3/4″), #10 (2″), #20 (2-1/4″)
A biscuit can contract over time, which can create a slight depression on the surface of the wood over the biscuit. To avoid this, cut your slots below the centreline of the board where possible, otherwise cut them about 3/8″ below the top surface.
The alignment marks on the fence and face of the joiner can become difficult to see over time. Use a permanent marker to highlight the marks.
Not all joiners come with a high-quality blade. If you’re not getting quality cuts (a lot of tear-out) upgrade to a quality aftermarket blade. Just like with your table saw blades, you’ll need to have the joiner blade resharpened from time to time.
Use the largest biscuit that you can (usually the #20) to get maximum joint strength. And don’t skimp – use as many biscuits as you can on a joint.
Keep your wood biscuits in an airtight container or bag with a packet of silica gel to prevent them from swelling. If they do swell, try popping them in the microwave for about 20 seconds or so just before you use them.