How to Make a Biscuit Joint

Updated: Oct. 04, 2023

Want to build a cabinet with joints that are both strong and invisible? Read this step-by-step guide on how to make a biscuit joint.

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Time

5-15 minutes

Complexity

Beginner

Cost

$100 - $200 if you don't already own a biscuit joiner & $10 to $20 if you do

Introduction

If you're interested in stepping up your cabinetmaking game by joining wood quickly, strongly and invisibly, you really should learn how to make a biscuit joint. Although the details of proper biscuit joining take some explanation, the basic principle is quite simple. A biscuit joint involves two pieces of wood invisibly fastened together with a thin oval of compressed hardwood (or more than one) and wood glue.

A biscuit joiner is a woodworking power tool that plunges a narrow groove into two adjoining pieces of wood. A thin, oval-shaped piece of compressed hardwood, called a biscuit, is then placed into both grooves with some wood glue. The grooves are of the correct depth to ensure the biscuit protrudes so it can occupy both grooves at once. With the biscuit and glue in place, the two workpieces are clamped together so the glue can dry.

Want to give biscuit joining a try? Good quality biscuit joiners are fairly inexpensive and easy to use. Biscuit joints can be done in several ways, but the most common and useful is the simple 90-degree joint used in cabinetmaking. That's what I'll be demonstrating here. Keep reading for a detailed step-by-step guide on how to make a biscuit joint.

Tools Required

  • Biscuit joiner
  • Eye and hearing protection
  • Pencil
  • Toothpick or skewer
  • Woodworking clamps

Materials Required

  • Biscuits of the right size for the job
  • Scrap piece of wood of the same thickness as workpieces
  • Wood glue

Project step-by-step (6)

Step 1

Choose biscuit size and adjust biscuit joiner

  • Select the biscuit size you need based on the thickness of the wood you’ll be joining. For wood 1/2 inch to 3/4 inch thick, I like #20 biscuits. For material 3/8 inch thick, #10 or #0 biscuits work better.
  • Rotate the numbered adjustment knob on your biscuit joiner to the number matching the size of your biscuits.
  • Rotate the small knob on the top of your biscuit joiner to adjust the height of the cutter. Locate the cutter as close as possible to the center point of your workpiece, so the groove you’ll be plunging ends up in the middle. Use your workpiece as a reference.

Adjusting Biscuit Joiner for making Wooden Biscuit JointRobert Maxwell for Family Handyman

Step 2

Plunge a test groove

  • Clamp down a scrap piece of wood the same thickness as your workpieces to your workbench, orienting it on its face (not on its edge).
  • Press your biscuit joiner against the edge of the scrap, then squeeze the trigger to turn on the machine.
  • Wait until the biscuit joiner reaches full speed, then slowly plunge it into the edge of the scrap wood until you feel it bottom out.
  • Retract and shut off the biscuit joiner, then push a biscuit into the groove you just made. If the biscuit doesn’t fit, it may have swelled slightly due to moisture in the air. Fix this by baking the biscuit in the oven for 15 minutes at 250 degrees.
  • Use a pencil to mark the edge of the scrap wood on the protruding biscuit, then remove the biscuit and reinsert it the other way around. If your pencil line just barely disappears, the depth of your groove is sufficient. If not, adjust the numbered knob to a slightly higher setting to increase groove depth.

Drawing a Mark on Wood with PencilRobert Maxwell for Family Handyman

Step 3

Prepare and mark workpieces

  • Determine which workpiece will have grooves plunged in its face, and which will have grooves plunged in its edge.
  • Mark a pencil line on the workpiece that will have a groove in its face where you want the top of the adjoining workpiece to go.
  • Lay the workpiece that will have a groove routed in its edge on top of the other workpiece, aligning its edge with the line you marked on the other piece.
  • Clamp the two pieces together and down to your workbench.
  • Draw a pencil line across the two pieces at each point where you plan to install a biscuit. A good rule of thumb is to place biscuits 1-1/2 inches from each edge and every 2 inches in between.

Drawing a Mark on Wood with PencilRobert Maxwell for Family Handyman

Step 4

Plunge grooves in workpieces

  • Lay your biscuit joiner flat on the workpiece and align the center mark on the machine with the pencil line you marked across both workpieces.
  • Plunge a groove in the edge of the topmost workpiece.
  • Orient your biscuit joint vertically, butting it up against the edge where you just plunged a groove.
  • Align the center mark of the joiner with your pencil line, then plunge a groove vertically in the face of the bottommost workpiece.
  • Repeat the procedure for any other biscuits you’ll need to complete the joint.

Plunging Grooves in Wooden with Biscuit JoinerRobert Maxwell for Family Handyman

Step 5

Do a test fit

  • Unclamp the workpieces, then clean out any sawdust from the grooves using a toothpick.
  • Push biscuits into all grooves, then dry fit the workpieces together.
  • Inspect the joint closely to ensure it’s tight.

Test Fitting Biscuit JointRobert Maxwell for Family Handyman

Step 6

Join pieces

  • Take the pieces apart again and remove the biscuits.
  • Drizzle a little wood glue┬áinto all grooves, then spread it around with a toothpick to coat the inner surfaces of each groove.

Spreading Glue into grooves in Wood with ToothpickRobert Maxwell for Family Handyman

  • Push a biscuit into each groove on one of the workpieces.
  • Interlock the pieces, then clamp them together tightly.
  • Allow the glue at least an hour to set before removing the clamps.

Biscuit JointRobert Maxwell for Family Handyman

FAQ

Are biscuit joints strong?

The answer is a resounding yes, with a few considerations. Biscuit joints are excellent for aligning and reinforcing the edges of two boards. They provide additional gluing surface area, making it harder for the joined pieces to pull apart. However, the strength of a biscuit joint depends on factors like the quality of the jointer, the type of glue used, and the accuracy of the joint’s fit. While they may not be suitable for heavy structural applications, biscuit joints are incredibly reliable for many woodworking projects, offering stability and durability that make them a valuable addition to any woodworker’s toolkit.

Can you biscuit joint plywood?

Yes, you can absolutely use biscuit joints with plywood. In fact, plywood is a popular material for biscuit jointing due to its versatility and wide range of applications. When working with plywood, biscuit joints can help align the edges of the sheets precisely and provide additional strength to your joints. This is particularly handy when building cabinets, furniture, or other projects where a clean, flush surface is crucial. Just ensure you’re using the right-sized biscuits and a high-quality biscuit joiner for the job.

How far apart should biscuit joints be?

As a general guideline, for typical woodworking applications, placing biscuit joints about 6 to 8 inches apart is a common practice. However, this spacing can vary based on factors such as the type of wood, the size and weight of the pieces being joined, and the overall design of your project.

For larger or heavier pieces, you may want to decrease the spacing to provide additional support and stability. Conversely, for smaller or lighter projects, you could space them a bit farther apart. The key is to strike a balance that ensures a strong and secure bond while also maintaining the structural integrity of your workpiece. Always refer to your project plans and consider the specific demands of your woodworking project when determining the ideal spacing for biscuit joints.