The plate (or biscuit) joiner is one those tools that gives a really big bang for the buck. In the hands of a seasoned professional or novice, it provides rock solid joints. For beginners, it is a tool that provides an immediate improvement in woodworking skills.

Early plate jointer

Before there were biscuits, a strong joint took a steep learning curve and more than a fair share of patience. Mortise and tenon joints requires exact mating surfaces. Spline joints require a router or table saw and the skill to cut the splines for a tight fit. Dowel joints require precision drilling.

Biscuit joints are not stronger than these methods, but when time and materials equals money, carpenters usually opted for glue and nails – often having the joint open up later, especially in trim work. Biscuit joinery made assembly convenient and it made a joint stronger then glue alone. The number one benefit of the biscuit in a glued joint is that it prevents movement, thereby reinforcing the adhesion provided by the glue.

The plate joiner has been around for 60 years, the brainchild of Carl Steiner, a Swiss woodworker, but the comparison between his invention and the tool we use today is like night and day. The first plate joiners were stationary units. Between 1956 and 1968 prototyped the portable plate (biscuit) joiner. Introduced into the U.S. in the early 80s by the Lemello Company, these early joiners were not much more than a angle grinder equipped with a small saw blade and an L-shaped.

The tool is fairly easy to use, despite its alien appearance.

Mark your work

Align the pieces you want to join, marrying the edges. Strike a line across the joint.
Use as many as you need. The type and size of the joint determine the quantity and size of the biscuits.

Cutting you slots

Set the depth dial to the size of the biscuit being used. Set the fence in the cutting position and adjust the blade height to about half of the boards thickness. Align the tools index line to the line scribed on the wood, make sure the face is flat against the wood, and fence flush with the top of the wood — turn on the tool and push into the wood. Plate joiners have a tendency to pull to the left as it bites into the wood, so it is best to put your thumb on the fence and hand on the wood to help counter the torque. The tool has non-slip pads on the facing that help stop any sideways movement. Both pieces of wood have to be cut.

Make your joint

After making all your cuts, blow the slots out so no dust or chips remain then run a bead of wood glue along the edges. Force some of the glue into the slots then slip a biscuit into each slot on one of the boards. Mate the board’s edges and clamp them together. The glue will swell the biscuits making a tight mechanical joint.

Endless possibilities

Once you get comfortable with the tool, you’ll find all kinds of ways to use biscuits. Consider…

  • Decking
  • Deck Railings
  • Attaching stiles to rails
  • Repairing damaged tongues in panels
  • Butt joints
  • Picture frames
  • Table tops and large panels
  • Attaching legs
  • Miter joints

Biscuits: One size doesn’t fit all

The best biscuits are die-cut beech imprinted with a pattern that promotes moisture absorption. Beech is the material of choice because it swells at a predicable rate.

Biscuits come in a variety of sizes, matched for specific jobs. The most commonly used are #10, #20 and #30 versions. Biscuits starting with “R” require a mini plate joiner.

The plate joiner is also a convenient mortiser for specialty items, like the UV-resistant deck board spacers/fasteners that allow deck boards to be evenly spaced and have the mechanical connection hidden or a the hinge that is shaped like a biscuit.