The right man for the job, the right tool for the task, are both important rules of conduct and work. We’ve used the latter often when writing about woodworking and the projects we undertake. The right tool for the task makes the task that much easier, of course.
The same concept holds true for joinery. You want strength when strength is needed; you want neat and square corners always, and you want those planks to be properly aligned when you’re making a tabletop for the dining room.
In short, you choose the joining method the project requires. Overkill on strength of the joint and method of making it isn’t necessary when all you are making is a picture frame. Shear strength isn’t required for those four mitered joints.
In fairness, though, larger frames that will hold a heavy mirror or tapestry might require something more than glue and some brads. We wrote recently about using pocket hole screws on mitered joints when extra strength is needed, and you will find that article here.
In this article, though, we are considering biscuit joints and dowels. Each has its place in joinery techniques, and the choice of which you will use on your project will depend on the project first and then on the work required of you, depending on the choice you make.
Biscuit Joints: When to Use, What to Consider
This form of joinery involves inserting a wood chip that is the shape of a football into a slot cut into both pieces of wood that are being joined. The slots are filled with glue, and the biscuit fits into the slots as the wood pieces are joined together. The biscuit will swell in size, and the two pieces of wood are joined.
The slot is cut by using a biscuit joiner or jointer, a woodworking tool with a small circular saw blade that creates a crescent-shaped hole. Careful measurements are made on each piece of wood to be joined so that the slots align perfectly. This will maintain a uniform and flush surface as the two pieces of wood are joined together.
Biscuit jointers can run in price from around $55 up to nearly $200, depending on the brand and the power.
Festool Domino: A Biscuit Joiner of Sorts
The exception to that price range is the Festool Domino. While not technically a biscuit joiner, the concept and process are very similar.
It works like a biscuit joiner in that it is a single plunge power tool. However, the cutting mechanism is different: a drill-like rotating cutter with a spinning bit that also moves sideways cuts a full-rounded mortise.
A corresponding mortise is cut in the second piece of wood to be joined, and a domino (much like a biscuit, although ridged and sized to match the cutting mechanism of the power tool) is glued up and fit into each of the mortise cuts as the two pieces are joined.
It’s fast, easy, and convenient. No other power tool and system can do what the Festool Domino does. It creates a very strong mortise and tenon joint, and the tool has become a favorite of woodworkers since its introduction to the market in 2007.
Dowel Joints: When To Use, What to Consider
Doweling, or making a dowel joint, involves drilling holes in two pieces of wood and using wooden pegs (dowels) in the holes to join the two pieces of wood together. The holes are glued up, the dowels are inserted into them, and the pieces are clamped together while the glue sets.
This method creates a strong joint (some woodworkers consider it the strongest joint, although we might disagree with that), especially when there are multiple rows of dowels.
Furniture makers, toy makers, shelving projects, and to reinforce butt joints – dowel joints are common among all of these. They obviate the need for nails, screws, and brads and help retain the integrity of wood grain in the pieces being joined. They will also help give the project a more professional look.
A doweling jig is used to help align where the holes will be drilled, and every woodworking shop has a power drill, so no special power tool needs to be purchased. Dowels come in a wide variety of dimensions, and the diameter of the dowel you use for the joint will depend on the project.
Doweling jigs can be found for less than $15 and up to $200, depending on the brand and size. Most are self-centering, making their use very easy and simple. They attach to the pieces of wood in such a way that they are already centered; jigs offer various drilling guide sizes, too, for any size dowel being used. Drill bits are guided both for location and for depth of hole.
Biscuits or Dowels: Which to Use and Why
Biscuits are a good joinery method when joining several planks for a tabletop or a shelf in edge joints:
- They help align the planks
- They provide additional gluing surface than not using them
- They hold tight over time.
There is the need for a biscuit joiner, though, an extra power tool in your shop. However, biscuit joiners are easy, simple, and quick to use, and the joints are not difficult in the least. The biscuits are made of either birch or compressed wood and are not expensive. Depending on the size, you can find a bag of 100 biscuits for under $6.
In those uses, there is not likely to be any shearing, so there is little pressure put on the biscuits. Their main benefit of use is the additional gluing surface for more strength and the neat alignment of the pieces being joined.
Dowels, while also used in the making of tabletops and shelving, require a bit more work. They are not as easy and quick as biscuits but require only the jig rather than another power tool in your shop.
However, dowels will provide much greater shear strength than biscuits. Looked at it another way, in edge joining (tabletops, for instance), you probably don’t need extra strength. With today’s adhesives, tabletop planks will hold well on their own – the advantage of using biscuits has to do with alignment, not additional strength.
But how confident would you be sitting in a chair that used only biscuit joints? Probably not as confident as you would be if the chair’s joints used dowels.
The comparison, though, probably doesn’t make a lot of sense, as they are simply good at different things. Again, the right joint for the project need. Each one gives you a reasonably quick and easy joinery method, and each one has its pro: alignment with a little bit of extra strength where it might not really be needed vs much more strength where it is needed.
We went searching for some video representations of the relative strengths of these two forms of joinery, and we found one. The videographer is one of us – a woodworking enthusiast who wanted to know the answer to relative strengths just like we did.
His results jibe with our sentiments on the uses of each form – biscuits for alignment, dowels for strength. It was interesting to see the relative strength of just a glue-up, too.
The right joint for the project remains another one of our mantras.