Biscuit joiners allow you to make solid precise joints, accurate enough to build fine cabinets. We show you the three key techniques you need to know—joints at right angles, joints in narrow materials and joints in thin materials.
By the DIY experts of The Family Handyman Magazine
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The advantages of biscuit joiners
The trick to successful biscuit joinery is cutting the slots in exactly the right spot so that the parts will line up correctly when they’re joined. Biscuit joiners have an adjustable fence that can be used to align the slot, but in this article we’ll show you a different technique. Instead of referencing the slot from the fence, we’ll show you how to reference the slots from the base of the tool. This method has a few advantages. It’s simpler to make an accurate slot because the tool is steadied against the workbench rather than the tool’s fence. Another advantage of this method is that you don’t have to readjust the fence for every cut. In this story we’ll show you how to use the bench reference method to join cabinet parts. We’ll show you how to join cabinet panels, face frames and 1/2-in. drawer material. You can use the same technique for any biscuit joint.
Technique 1: Join plywood with the bench reference method
Photo 1: Mark the biscuit positions
Align the two parts to be joined end to end. Then number the parts and draw pencil lines where you want biscuits. In our example, the lines will be inside the cabinet.
Photo 2: Rest the base of the joiner on the bench
To cut accurate slots, rest the biscuit joiner on the workbench instead of the fence. It’s more stable and doesn’t require any setup.
Photo 3: Hold the panel with a right angle support
The support keeps the panel steady and at an exact right angle. Then use the same method of resting the base of the biscuit joiner on the benchtop to cut the slots.
Photo 4: Add glue and biscuits
Brush glue into each slot. Then slide biscuits into the slots. Brush glue into the slots on the second panel before you joint the two.
Photo 5: Fit the panels and clamp
The base of the biscuit joiner and the panels were against the bench top when the slots were cut, so the joints will line up perfectly.
Photos 1 – 5 show the steps for joining 3/4-in. plywood without using the fence. On most biscuit joiners, the slot will be pretty close to centered when you use this method. But even if the slot is a little off-center, it’ll still work fine as long as you orient the biscuit joiner and pencil marks as we show in the photos. Here are a few tips to ensure perfect joints:
Work on a flat surface. The top of a table saw or a solid-core door is a good choice.
Clean sawdust off your work surface before each setup.
Hold the base of the biscuit joiner and the workpiece tight to the work surface as you cut the slots.
Cutting Slots Without the Fence
All biscuit joiners feature a fence that can be adjusted up or down and pivoted at varying degrees for cutting slots in beveled edges. Some woodworkers prefer not to use the fence when cutting slots. Instead, they use various spacers and jigs to cut accurate, consistent slots every time with far less hassle. For most of the tips we show, the adjustable fence is simply locked in the upright position.
Technique 2: Support narrow face frame parts against a block
Photo 1: Use a template to align the slot
Cut a biscuit slot in a scrap of wood and mark the center and the size of the slot, in this case No. 0. Now use the template to position the biscuit mark. We offset this slot to the top where the protruding biscuit can be cut off and the slot won’t show.
Photo 2: Screw plywood to the bench as a clamping aid
Line up the end of the part with the end of the clamping board and clamp the two together. The wide end makes a stable surface to press the biscuit joiner against.
Photo 3: Cut the side slot
Align the center marks and cut the biscuit slots. The clamping block makes a solid surface to push against.
Photo 4: Assemble the face frame
Spread glue in the slots and insert the biscuits. Align the parts and clamp them. When the glue dries, cut off the protruding biscuits.
It’s tricky to cut slots in the ends of narrow parts using the biscuit joiner fence. The small surface area makes it hard to hold the biscuit joiner stable. But it’s easy to cut accurate slots in narrow parts using the bench reference method. The photos here show how. We also show how to cut the biscuit slots off-center so the biscuit will protrude on one side only. This is handy if you want to join narrow parts and the biscuits are too large.
Technique 3: Make biscuit joints in thin material
Photo 1: Label parts and mark biscuit locations
Avoid confusion by carefully labeling all the parts. Then mark where you want the biscuits.
Photo 2: Don’t adjust the fence—use spacers
Instead of adjusting the fence to cut slots in thinner material, add a spacer underneath. You’ll get great results as long as you use the same spacer when you cut the slots in the adjoining panel (see Photo 3).
Photo 3: Place the spacer under the end of the panel
Make sure the spacer doesn’t protrude past the face of the panel. Then rest the base of the biscuit joiner on the workbench when you cut the slots.
Photo 4: Glue and biscuit a perfect joint
Since both parts were held up the same amount by the spacer, the parts will line up exactly when you assemble them with biscuits.
You can use the same bench reference method to cut slots in material thinner than 3/4 in. by placing spacers underneath. Subtract the thickness of the material from 3/4 in. The difference is the spacer thickness. We show cutting slots in 1/2-in. plywood drawer parts. Without the spacer, the slots would be too close to the edge. But with the spacer, the slots are nearly centered. Photos 1 – 4 show how.
Video: How to Use a Biscuit Joiner
A biscuit joiner will help you make strong, fast and accurate joints. Spike Carlsen, an expert at The Family Handyman, will show you how to use a biscuit joiner to get perfect joints.