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One of the most common activities to face during a woodworking project is the union of 2 boards of wood. There are plenty of alternatives to do this: mortise and tenon joints, tongue and groove joints, half-lap joints, and the list goes on. Much depends on what you want to get from the joint itself.
A possible alternative is the so-called “biscuit joint”, which requires a biscuit joiner. This power tool comes with a small blade that creates an oval slot inside the wood to place the biscuit in. The latter is a compressed wooden bit of appropriate shape. Everything is consolidated with the use of glue, which soaks the biscuit and makes it swell, solidifying the joint.
Biscuit joints are very easy to make, so they are also perfect for a beginner who is approaching woodworking. They are suitable for a variety of projects, like tabletops, cabinetry, and more.
If you are thinking about adding a biscuit joiner to your tool arsenal, it is certainly a good idea to want to learn how to use it to its full potential. In the following paragraphs, we will go through some key tips to get the most out of your biscuit joiner.
Biscuit Joiner Tips and Tricks
Choose the Right Reference
The most important thing is having a solid reference when using the joiner to get a clean, precise cut. Even a little shift can make your slot uneven. You absolutely want to avoid that: the biscuit must fit perfectly inside the slot to get a solid joint.
There are two ways to guide the tool: you could either referencing with the adjustable fence or the machine base. I try to use the latter as much as I can since it guarantees good repeatability. If you want to use the adjustable fence, keep it down with one hand to avoid cutting the slot wrong. Make sure to use the same reference edge when cutting, or else the slots won’t align.
A quick suggestion: make sure to reference off the visible surface. That way, you’ll get a flush finish exactly where you want it.
Get a Glue Brush!
This is a key aspect. Uneven glue application leads to uneven biscuit swelling. As a result, the jointed board might be misaligned. Glue application is very important to get a flush finish.
To get a good result, use a brush to uniformly apply the glue to the slot. I like to glue one slot, place the biscuit in, then also glue the part of biscuits that comes out. Put a good amount of glue. I usually glue the whole joint, then sand the excess away once it dried out.
Looking for a glue brush? I really like silicon models like this one, mainly for two reasons. Glue coverage is very good; they are very easy to clean: some hot water is enough. Or you could simply let the glue dry and then peel it off. No more throwing away horsehair brushes after a single use.
Obviously, using the right glue is essential. For the average DIYer, the choice should come down to either PVA (polyvinyl acetate) glue or polyurethane glue. There are 3 categories of PVA glues: type I (waterproof), type II (water-resistant), and type III (non-water resistant). The first two are ideal for outdoor use, while the latter due to its characteristics is perfect for cabinetry. All of them make for very strong joints, and they can be sanded once dry with good results. I really like to use the Titebond III (which is a type I despite its name) for both indoor and outdoor use.
Polyurethane glues are very good for non-wood materials such as plastic and ceramics. They provide a bit less strength than PVA glues, but more than enough for a DIY project. They are the best for finished projects. Since they are not water-based, the wood pores are more prone to receive finishes.
How to Make Side Joints?
Joining boards is relatively easy. What about side joints? I’m talking about joining two boards at a 90 degrees angle. Things can get a bit tricky if you don’t use the right setup. There are a lot of ways to do this. For example, you can use an L-fence made of a couple of boards joined together. Place your working piece inside, against one side, and use the other as a reference surface for the biscuit joiner. This way, you will be referencing off the tool base which guarantees correct results. Hold the fence with your hand or clamp it to your workbench. If you don’t want to use a fence, simply clamp a stud on your bench and reference off that.
Let’s talk about a possible scenario where you need side joints: putting a fixed shelf inside a cabinet to strengthen it. The problem here is that you need the biscuits to line up from a side all the way through to the other one. A quick solution here would be using a simple spacer. Align it with one end of the piece and then reference the biscuit joiner off that. Be sure to clamp the spacer the to same end on the other side.
Biscuit Size – Choose the Right One
A frequently asked question is about the right biscuit size to use. There are 4 types available: #0, #10, #20, FF.
The first three are the most common ones, going up in size from 0 to 20, ovally shaped. FF (face frame sizes) are even smaller than #0, which makes them perfect for smaller projects. Be careful, though: they have a circular shape, so you need to be able to change your joiner blade to cut the right slot for them. Not all the biscuit joiners let you do that.
So let’s talk about the right size for your project. The main thing here is if you want to obtain strength or just alignment from your joint.
If you want to use biscuit joinery just to keep things aligned, the smallest the better here. You also gonna be fine using bigger sizes, whatever you have available is fine. On the other side, if you are looking for strength, you want to use the bigger biscuits you can fit without compromising the integrity of your project. A good rule of thumb here is for the slot to be at least at a quarter of an inch from the closer uncut wooden edge.
The next question that arises is how many biscuits you should use to get the job done. For alignment, you don’t need a lot: a couple of biscuits per foot is enough. On the other hand, you want to use as many as you can if you require a strong joint. If you want to space them evenly, put them at 6 to 8″ from the center to one another. Spacing isn’t that important. Just make sure you leave a little bit of room between them so you don’t overlap the slots.
More Biscuits Tips: Size Testing and Storage
As I mentioned earlier, using the right size is key. Not only in an absolute sense, but also in relation to the slot dimension. What I mean is that the biscuit should fit just right inside the cut. To check this, put the biscuit inside the slot dry. Then turn the board upside down: a biscuit with a good fit shouldn’t fall from the slot. The resulting connection will be even more solid when you’ll apply the glue and the biscuit will start swelling.
Swelling is very important to get a firm joint. There’s a downside to this: biscuits also absorb air humidity, so you could end up with a whole box of ruined biscuits if you don’t store them properly. To avoid it, keep them in a firmly closed jar or use desiccant packs that will absorb any moisture excess.
Need More Strength? Use a Double Biscuit Joint
If you want to make your joint even stronger, you should consider a double biscuit joint. There are two ways to obtain this. If your board is wide enough, create two slots aligned, on top of each other. To space them appropriately, you could either flip your piece or use a gauge.
If you cant create a separate slot because the board is too thin, cut a double slot to fit 2 biscuits in. How to do that? Cut the first one, then put an appropriate-sized spacer under your tool’s base. This will raise the blade to the right amount to create a bigger slot. Sometimes the spacer comes when you buy the tool. However, you can easily make one with scrap wood.
How to Use a Biscuit Joiner At a 45 Degree Angle?
Creating a biscuit joint at an angle is very easy. Simply set the adjustable fence at the right angle, for example, 45° or 30°. Keep the fence still using one hand, while pressing on the handle with the other. Make sure to use the same reference surface for both pieces to join, either internal or external, to make sure the slots correspond. If your biscuit joiner comes with a spacer, you should use it to get better slot positioning in the middle of the board. Use an angled fence to clamp your stock so it doesn’t move while it dries.
Finally, use fitting biscuits to make sure your joint will be as strong as possible. This is even more important with miter applications like these.
Dust Extraction (and Some Safety Tips)
Things can get a bit messy when using a biscuit joiner. This is especially true when cutting side joints holding your tool perpendicular to the workbench. You should use dust extraction if possible. Most of the models come with a dust bag. Even better if you have a dust extraction system in your workshop. On top of that, always wear some safety glasses.
Talking about safety, biscuit joiners are one of the safest tools you will find in a shop. The rotating blade stays hidden all the time, and it just comes out when pushing into the board. So you really need to make an effort to cut yourself. However, just to be safe, you should avoid putting your hand in front of the tool (for example for holding down the board). Keep them aside.
Another important tip is to clamp down your pieces when cutting slots. Not only you’ll get better results, but you’ll also avoid possible incidents.
So there you have them, my top 10 biscuit joiner tips. As you’ll see when you’ll start using them, biscuit joiners are very safe and straightforward tools. Let’s summarize them:
- Use the tool’s base or the fence for reference. This is key to avoid cutting errors;
- Use a brush to lay down the glue the slots and get a solid joint;
- Build yourself an L-fence to cut side joints without hassle;
- Choose the right biscuit size, generally the bigger the better;
- Compare the size of the biscuit to the slot before putting any glue into it;
- Keep your biscuits dry!
- Consider using a double biscuit joint if you need more strength;
- To cut at an angle, simply use the adjustable fence;
- Use dust extraction (and wear glasses);
- Don’t forget about safety! clamp your pieces and keep your hands aside from the blade.
Keep these things in mind and you’ll get the hang of it very soon!