What Is A Biscuit Joint?

(Last Updated On: December 19, 2020)
Woodwork is installing and glueing a biscuit joint.

A Biscuit Joint is made up of pieces or flakes of wood that are compressed into an oval-shaped chip that is processed through a Biscuit Cutter. These are inserted in grooves made by a Biscuit Joiner to connect or join two pieces of wood by the edges or sides. A biscuit joint is usually made out of beech wood. 

The biscuit is inserted in a cut made by a Biscuit Jointer, it is glued in place, and then, the glue’s moisture expands the biscuit and tightens it in place. 

How Does Biscuit Joint Works?

Biscuit joinery is one of the basic wood joining techniques in woodworking. It makes use of the small wooden piece as a tool or medium to join the side or edges of wood and is usually used in joining tabletop planks. 

Biscuit joints are used to strengthen the joints of two pieces of wood, but it is much more useful as alignment aids in connecting pieces of wood for furniture. 

A biscuit joiner is a tool that has a router that enables a slot cutter or blade to create a slot for the biscuit. Its sole purpose is to plunge a thin, same as the width of the biscuit, crescent-shaped hole on ends or edges of wood enough to fit half of the biscuit on the first panel and another half on another side with a matching slot. 

Beginner Tip #1: As a beginning woodworker, you must also ensure that the cut from your biscuit joiner is somewhat deeper than half of the biscuit, yet enough for each half to occupy the matching slots on each wood for the adjustments later on.

So, to be able to join, for example, two pieces of wood as a starting piece for a tabletop, one must align the boards side by side, lateral to the length, and mark the points where the biscuits will be inserted. Use the biscuit joiner to cut in the middle of each edge or side of the wood plank. Next, apply glue to each side of the biscuit before inserting it into the slots and put together, matching the slots on the other board. 

Beginner tip #2: Mark cut faces. Although this is for obvious reasons, marking cut faces aids as a foundation in the process. Having a reference board for marking also helps a great deal for positioning.

Simply to say, it doesn’t take long for a beginner to master the use of the biscuit joint, though to be able to produce woodcrafts with the use of biscuit joint effectively depends on many factors. 

The most crucial part of utilizing this method is alignment. It is its strength, and the application of this is also its bane. A poorly aligned biscuit joint will render the method useless and wasteful. Though to prevent this from happening, some biscuit joiners have an in-built measuring gauge and scales as a guide, though it would be best to measure from the wood that you will use for the project in configuring the standards. 

Pro-tip #1: Mark reference edges for effective alignment. With the biscuit jointer, it can already be used as an alignment edge. You can scale and make reference marks with the bottom or the fence. 


Application & Uses of Biscuit Joint

As was mentioned before, the example described an Edge-to-Edge joint, which is the primary and most common technique for the biscuit joint. The edge-to-edge joint is used to connect wood with matching width in making a tabletop formation connected on the long edges. 

Beginner Tip #3: Hands away from the blade path. Of course, one should monitor precautionary measures in handling tools, especially since most of the woodworking tools concern cutting and drilling. For some biscuit joiners, there is an in-built mechanism that automatically retracts the blade once it is pulled away from the wood. But, for added protection, you may clamp pieces wherever possible. 


Biscuit Sizes

Aside from the edge-to-edge joint, biscuit joints are used in other wood joinery methods. There is a range of measurement for biscuits, shown below are three in comparison to sizes-small, medium and large: 

  • #0: 5/8 inch by 1 3/4 inches
  • #10: 3/4 inch by 2 1/8 inches
  • #20: 1 inch by 2 3/8 inches

Measurements of the biscuit vary in increments of 5 from #0 to #20. the smaller biscuits are useful for aiding miter joints connected by beveled cuts on wood boards. Another is the end-to-face or T joint, wherein the end grain or edge of the wood is linked to a side or face of another wood. 

Beginner tip #4: Spacing between biscuits are advised to at least be around 200mm.

Most of the projects using biscuit joints make use of the bigger biscuits since they add more strength. Knowing the size of the biscuit that you’ll utilize in your project also needs adjusting on the biscuit joiner itself since the depth of the cut will vary on it and must ensure that exactly half of the biscuit is inserted to each wood. The bigger the size of the biscuit, the deeper the plunge of the blade.

Pro-tip #2: When having the boards laid out side by side, make sure to position each board’s end grain opposite of the other, making them in an alternate pattern. This will aid the end product’s stability by the time the wood widens or shortens.


Why Biscuit Joints? The Pros and Cons

Pros 

Connecting two pieces of wood is the first challenge in a woodworking project. No matter the project is joining pieces of wood by edge grain, end grain or face grain and keeping them intact through a long period is one of the fundamental aims of wood-crafting in instilling quality. 

The tricky part appears especially on this part of woodworking since the end grain of the wood is hard to join with another surface since it is porous and often rough, which makes it a primary challenge in woodworking along with choosing among the numerous wood joint types and techniques. Using biscuit joints to support a simple butt joint is very effective in connecting the end grain of the wood with the face or edge grains not only for alignment but adds a considerable amount of strength. With glue alone, there is also a hassle with making use of multiple clamps and waiting for the glue to dry for hours. While with the help of the biscuit, it already fixes it in place, therefore butt joints using glue only are proven to be ineffective.

And this brings us to biscuit joints, one of the basic joining methods in woodworking. A lot of comparison in strength, ease, and versatility are argued and debated. Compared with other joint configurations such as miter joint, butt joint, T joint and corner joint, a biscuit joint is undoubtedly an optimal choice. 

Between a wood dowel and biscuit joint, they are both used to join two pieces of wood conveniently and conceals the method of joinery but still ensures and aids in strength and alignment. So how are biscuit joints better? 

Biscuit joints are known for their usefulness in alignment more than dowels and, when done right, also adds some strength. In some biscuit joiners, cutting a slightly oversized slot for the biscuit makes it easy to adjust before having it fixed with glue, which makes it a doable method. 

Beginner tip #5: Use dust extraction. This makes a convenient addition to the tool to clean up shavings and debris from the get-go.

Cons

In general, there is no perfect method of joining materials in woodworking. Joint configuration varies on each project and a case-to-case basis. 

On this matter, there are disadvantages to using biscuit joints. 

There has been a considerable amount of discussion regarding whether a biscuit joint is more or less useful than other joinery techniques in woodworking like the lap joint, butt joint, touch and groove, and others. It also garnered the attention that it was only made popular by a woodworking tv show back in the day called “The New Yankee Workshop,” and some speculated that the use of a biscuit joiner is cheating, but that is far from the case in the usage and usefulness of the tool objectively. Despite this, many woodworkers have trusted the use of this technique in many projects, both on-the-job and for personal outputs. 

Usually, the problem with the application of biscuit joinery in woodworking lies simply on its usage. This includes the following cases:

1. When the biscuit is poking out or exposed which defeats the purpose of concealing the joinery method; 

2. Misalignment of the panels wherein there is an inaccuracy before or during application; 

3. Slots are deformed which is either a machine malfunction or inaccuracy in the scale, and 

4. Weakening along the seams where glue has been applied. 

In comparison to other joinery methods and tools, biscuit joinery is not very much dependable on strength. For example, wood dowels are known to be dependable in joinery because of the strength it gives to joints and only makes use of a drill and dowels. Therefore, this renders the biscuit joint unsuitable for heavy-duty woodworking projects. 

Besides this, biscuits joiners are too specialized a tool. They are not recommendable as a starting tool for novice woodworkers, keeping in mind other basic and easier joinery methods to apply without purchasing another item.

This gives a setback to biscuit joints since it needs a special tool for cutting catered, especially into the designed shape–the biscuit joiner. Along with its limited usage, this makes the biscuit joint rarer than its Wood joinery counterparts though it is known instead for aiding in arrangement and support. 

Biscuit joinery is much more prevalent among Finish carpenters on job sites like for installing frames and touch-ups.


Conclusion 

In conclusion, biscuit joints are specially designed to effortlessly organize and support the alignment of panels and frames in woodworking and give a considerable boost to other joinery methods that require aid. In comparison to Dowel Joints, this is a quicker method and is seen as a practicable substitute for a Mortis-and-Tenon Joint if slots are a way to go. When the application of a biscuit joint is done right, its strength is comparable to that of the Mortis-and-Tenon joint and Dowel Joint, if not, definitely sturdier. 


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