The Basics of
            Biscuit Joinery


Learn how to make your biscuits joints stronger, faster and more accurate with a biscuit joiner!  There are six basic joints and we will review how to make them.  Biscuits can add strength to a joint, such as when you join a table apron to a leg. They can be used as an alignment aid when you glue up a tabletop. In a solid top they reduce the time you spend leveling your joints.  They really shine when you glue veneered panels together, as they keep the panels in line and you don’t end up sanding through the veneer.

Biscuits are available in three sizes #0, #10 and #20.  It is a good rule of thumb to use the largest biscuit size that will physically fit in the application.  Unless you are joining narrow face frame or picture frames or using ” or thinner stock, you will find the #20 biscuit size to suit most applications.  After selecting the biscuit size, set your joiner’s depth adjustment to the correct size.  Also, be sure that is set properly as you do not want to discover during glue-up that your biscuit slots are not deep enough.
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Some of the more common biscuit joinery applications are shown below and we will review how to do them

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Panels

This is the simplest of the biscuit joints and the most common.   Lay out you panel or top and select the best grain pattern.  Start with spacing the biscuits 2”/3” in from the ends and 6”/10” apart for the balance.   Mark them with a pencil line. Set the height adjustment to position the biscuit in the center of the stock.  Make the cuts, glue, assemble and clamp the joint.

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For stock that is 1” or more in thickness, you may wish to use double biscuits at each location.  Set the location to assure that there is at least 3/16” of material between the biscuit and the outside and between the biscuits themselves.

Face Frames

Face frame joints are an ideal application for biscuit joinery. Using a joiner you can create a very strong, precise joint that is much faster to make than a dowel or mortise and tenon joint.  This is an excellent joint as long as your stock isn’t too narrow.  A #0 biscuit will work only with stock as narrow as 2 3/8”.  Any narrower and the biscuit will poke out the sides.  In some applications this will not cause a problem.

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Corner Joints

In casework this is the classic joint for a joiner.  Lay out the positions of the pieces to be joined.  Select your biscuit size and set your fence to 90 degrees centered on the stock thickness.  For this joint, you will make cuts into the edge of one work piece and the face of the other.  The edge cut is performed the same as the edge-to-edge joints as we did with the panel technique.  The face is made by clamping the work piece and aligning the tool to the edge of the face of the material.  Make the cuts, glue, assemble, and clamp the joint.

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Off Set Joints

In casework it seems that there is always a need for the offset joint.  Do your layout for the biscuits using the same rules as before.   Select the work piece that will be set back and adjust the fence height to center the cut in the thickness of that piece.  Next, adjust the fence up by an amount equal to the desired offset.  Make the cuts and glue assemble, and clamp the joint.

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Edge Mitered Joints

One of the very best ways to join edge-mitered pieces is with a biscuit joiner.  When building our Hope Chest Combo’s it is a quick perfect joint.  This joint hides the end grain.  It offers added strength as well as ease of assembly.  Position your work pieces and layout the biscuits locations of the outside of the joint.   Clamp the piece and make the cut into the mitered edge.  Cut all the joints and assemble with glue and clamps.

 

Mid Panel or T-Joints 

Biscuit joining is an alternative to dadoing when making a T-joint. This method will work well with material that is at least 5/8” thick. The best way to insert a shelf into the middle of a panel is to use the shelf itself as a fence for the biscuit joiner. First, mark the shelf on the panel where you want it to be placed.  Lay the shelf on the panel and clamp together.  Mark the biscuit locations.

 

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Set your fence angle at 0 degrees and some jointers will require that you remove the fence.   Using the bottom registration surface align the tool with the biscuit location marks and make a vertical and a horizontal plunge cut for each biscuit location.  Glue, assemble and clamp the joint.

Not much goes wrong with a biscuit joiner.  If you mess up a joint insert a biscuit with glue and trim to fit.  Then re-cut the joint.  Like router bits and saw blades the blade can gum up and WD-40 or kerosene will clean it up.  Replace the blade when it starts to burn the material.  Dust collection can be a problem as most joiners are weak in this area but keeping the bag clean will help. 

Brian Murphy
American Furniture Design Co

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