I can’t remember the last time the woodworking community has been so abuzz about a new tool as I have seen with the eminent release of the Festool Domino® Tenon Joiner. So what’s the buzz all about? Well, imagine being able to cut mortises for mortise-and-tenon joinery as easily as using a biscuit joiner.
The Domino tenon joiner is a revolutionary and evolutionary tool for the woodshop that cuts mortise slots for mortise-and-tenon joinery. What makes the Domino joiner unique from many other power tools for mortise-and-tenon joinery is that you bring the tool to the work, instead of bringing the work to the tool. This is very handy for larger projects, and is one of the primary reasons for the popularity of biscuit joiners.
What separates the Domino joiner from a biscuit joiner is the type of joint and the versatility. The Domino tenons come in five sizes ranging from 5mm (3/16") thick to 10mm (3/8") thick, and the joiner plunge depths range from 12mm (1/2") to 28mm (11/8"). Compare this to biscuits, which are 4mm (5/32") thick and penetrate into the workpiece a maximum of 12mm (1/2").
While a biscuit is loosely considered a spline, a Domino is a true floating tenon. The primary distinction is the orientation of the grain and the depth of the penetration. The wood grain of a biscuit is slightly off-axis from being a true spline, but it is nevertheless predominately in-line with the joint. A tenon achieves its strength because the grain of the tenon is perpendicular to the joint.
Domino works by plunging a rotating and oscillating mortising bit into the wood. The bit rotates at about 20,000 rpm and oscillates side to side at about 900 sweeps per minute. The significance of the high sweep speed is that the bit is cutting on the tip as it plunges inward, instead of cutting from the side, like a router bit does. Cutting on the tip means the bit will be less prone to deflection, and therefore, cuts cleaner bores. This also results in a longer cutter life. As a matter of fact, Festool states that the mortising bits should last between 4,000 and 10,000 plunges before they need to be sharpened. This long cutter life is because the bit stays fairly cool throughout the plunge.
Users that are familiar with biscuit joiners should feel right at home with using the Domino joiner. Many of the controls and settings are similar to a biscuit joiner. The height of the fence adjusts to control the vertical position of the tenon, the angle of the fence adjusts for mitered joints, and another setting controls the depth of plunge.
Unique to Domino is that the width of the tenon slot is adjustable. The mortise width setting allows you to make the slots wider than the tenon for misalignment correction. One application for this is edge joining long boards. The first tenon slot is made tight for lateral positioning, but subsequent slots are elongated to make it easier to align each slot. Domino even has a set of optional outrigger guides with adjustable alignment pins just for this purpose.
Another intriguing application is to help account for cross-grain expansion, such as breadboard ends. The mortise in one board is made tight, but the mating mortise in the adjoining board is made wider to allow the pieces to move laterally with expansion and contraction.
THE MORTISING BIT sweeps side to side as it plunges into the wood.
The Domino tenons come in four thicknesses for a wide range of joint sizes. Each tenon size requires a different mortising bit. Even the mundane task of changing the mortising bit was made elegantly simple. The whole fence of the joiner slips off the motor housing with a quick release lever, exposing the bit for easy changing. You just press the spindle lock and unscrew the bit. Changing mortising bits is surprisingly fast and easy.
This may sound a little silly, but one of the nicest things I like about the Domino is the power switch. It is just so perfectly designed, and I have seen my share of poorly designed power switches. With just a flick of your thumb you can turn the joiner on or off. There is no fumbling with a trigger lock, and it is positioned right in front of your thumb position.
The Domino also has spring-loaded guide pins near the mortising bit for aligning the mortise slot without needing to mark the location first. These are used to accurately register the mortise relative to the side edge of a board, or from a previous mortise slot. These pins are perfect for making small boxes, such as drawers, but they are a little too far apart for making face frames, where the primary stock is 2" wide.
THE FENCE BODY is easily removed from the motor housing for quick bit changing.
THE GUIDE PINS align the mortise 37mm (17/16" ) from the edge of the workpiece.
Precision placement of mortises
One of the most unique aspects about the Domino joiner is how precise the tenons fit into their mortise slots. Because the tenons are not compressed, they are more accurately sized, and therefore, so can the mortise be more accurately sized. The result is that the tenon fits very snugly into the mortise every time.
A snug fit is critical if the tenon is going to be used for alignment purposes, because any slop or play in the mortise can result in twice that amount of misalignment in a joint. I stopped using biscuits for alignment years ago because I couldn’t get consistent results with every biscuit. I just completed a large project where I used over 300 Domino tenons for alignment, and every single one of them was spot-on.
Looking under the hood
I still remember that cold and rainy day in November of 2005 when I opened my e-mail inbox and found a message from Festool with just the one-word title, “Domino.” I had no idea how it worked, but I knew I had to get my hands on one. It was an agonizing three months to wait, but the first Domino to enter the country had my name on it; well, sort of. Call it a cruel joke, but somebody had cut the motor in half (see photo above).
Actually getting a cutaway model wasn’t so bad, because as an extreme tool junkie, one of the first things I usually do with a new tool is take it apart to see how it works. That’s also how I typically approach a product review too; I examine a tool from the inside-out to be able to tell woodworkers things about tools that they can’t see by looking at one on a store shelf.
In typical Festool fashion, the Domino joiner is built for long life and precision. One of the first things that people don’t notice about the Domino joiner is that its motor is spinning at an amazing 25,500 rpm. The reason why this isn’t immediately noticed is because it doesn’t sound like it is spinning as fast as a router. I have never heard a tool that spins this fast be so quiet. A typical biscuit joiner motor operates at less than half this speed, yet is much louder. Domino is so quiet because of the precision of the design.
Most right-angle tools, like biscuit joiners, have right-angle gearboxes that sound like rock crushers when they rotate; it’s not a very pleasant sound. On the other hand, the Domino gearbox just seems to purr. The primary drive on the Domino joiner uses a very shallow-angle, spiral-bevel gearset. This is very quiet because the gears lash together in a graceful curving motion, instead of the slap-slap-slap of a typical straight-bevel gearset. Conversely, at the business end of the tool where power and stress are high, a straight ring-and-pinion gearset provides great strength and long life. The choice of the gear styles was well planned and provides the greatest strength where needed and the quietness where it matters most.
Precision is due to bearing selection
One of the most common comments you may hear from people who have used the Domino joiner is how precisely it cuts mortise slots. Several years ago I performed a thorough tool test on biscuit joiners, and virtually every joiner my team tested had runout (wobble) in the blade, and slot thicknesses varied from cut to cut. This is why many woodworkers have problems getting flush joints with a biscuit joiner.
With the Domino, there is no wobble; there is no runout. Every cut is just like the previous one. Why is this different? It’s all in the bearings, and you won’t find bearings like these in other tools. The main sweep bearing has an amazing 21/2" diameter. That’s larger than the diameter of the arbor bearing on my table saw! The larger the diameter, the more stable the rotation will be, and in this case, the less runout the sweep will have. Also contributing to the stability of the cutting motion is the 5/8" tall needle bearing on the center of the ring gear shaft. As a matter of fact, most biscuit joiners have a single ball bearing at the bottom of their vertical arbor shaft and a bronze bushing at the top of the shaft. The comparable shaft in Domino has two roller bearings plus the aforementioned needle bearing.
The top half of the gearbox is the most complicated, and is dedicated to controlling the sweep width of the mortising bit. The oscillation yoke pivots back and forth as an eccentric cam rotates. The different sweep widths are obtained by moving the pivot point of the yoke.
Putting Domino to work
Using the Domino joiner is very easy, and the variety of applications is nearly endless. A cabinetmaker, for example, could use Domino throughout the entire building process for making cabinets; from faceframes to carcase construction, drawer boxes, and even for alignment between cabinets during installation.
I’ve seen some pretty innovative and thought-provoking uses for Domino coming from the minds of furniture makers in Australia, where Domino has been available for almost a year. Building a bed, crib, or chair that uses a lot of slats in the construction can be a daunting task for any woodworker, but I have seen a couple of examples where the slats were sized so they could fit directly into a Domino mortise without the need for a tenon. David Dundas (see Zigzag Chair project on page 38) showed me one such example he used for installing curved slats in one of his rocking chairs. He made the curved back slats by laminating thin strips of wood in a curved form, and then shaped them to the same size as the Domino mortise.
A stunning example of just how far you can take Domino joinery is Gerry Coon’s handmade kayak. Scarf joints are a common method that boat builders use to join short boards into longer boards. Gerry augmented the strength of the standard scarf joint by making it a tenoned scarf joint using Domino tenons. These were used to fabricate the 16' gunwales of the kayak.
Gerry also used the Domino mortise slot for securing the kayak ribs into the gunwales. He shaved the ends of the ribs with a block plane to match the medium width setting on the joiner. Gerry says that using the Domino joiner was a significant time-saver for cutting all of these mortises.
The bottom line
If you are in the market for a used biscuit joiner, this is the time to buy, because I think there will be a lot of them on the market after Domino hits the shelves. Some will argue that Domino won’t make a biscuit joiner obsolete any time soon, but there is not a single task that I can think of that Domino can’t do better than a biscuit joiner. Moreover, there are a lot of tasks Domino can do, that a biscuit joiner just cannot do.
The only argument against Domino is the cost. Many woodworkers will have a difficult time justifying the $700 initial outlay ($660 introductory price until May 31, 2007), but for the avid hobbyist or professional woodworker, the tool will pay for itself quickly in time saved.
—Rick Christopherson has been using the Domino joiner for more than a year while writing the North American owner’s manual for Festool. For the past several months, he has continued to use the tool extensively in his own workshop.
His current woodworking project is a complex expanding round table that has nearly 325 Domino tenons. Below, RIck is pictured fabricating the lower base of the table. The joints will support the entire weight of the table, estimated at 500 lbs.
Rick is a technical writer, engineer and cabinetmaker.