Matthew Schenker
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Using the Domino to Make a Padauk Mirror
I just completed a makeover for the entry area of my old house (patching walls, stripping and repainting all the old moldings and other woodwork, refinishing the fir flooring). When it was all done, my wife and I decided to have a mirror on the wall. Padauk was our wood of choice, since its red color would add a nice touch as you walk into the house.
I wanted to use the Domino for the mirror mortise-and-tenon joinery. But I also wanted to set the mirror into grooves, instead of using rabbets. It didn't take me long to realize there's an easy way to use the Domino to cut the mortises and tenons, and then use the Domino mortises as aids in cutting the grooves for the glass. It's such a simple thing, I decided to document the process. Along the way, I realized this is also a good opportunity to review the various settings and aspects of the Domino.
Preparing the Wood
I started with padauk that was about 1" thick, and milled it into four pieces each 2 1/8" wide and 7/8" thick using my jointer and planer. I ripped the pieces on my bandsaw.
Below is a shot of the four milled padauk parts, set out on my MFT 1080:
Domino tenons come in a range of sizes (in millimeters):
- 5x30
- 6x40
- 8x40
- 8x50
- 10x50
Based on the thickness and width of the mirror parts, I decided to use 8x50mm Domino tenons. This would form a tenon in each member is about 1"-deep by 11/32" thick by 7/8" wide -- plenty strong enough.
Festool sells an assortment of Domino tenons, which come delivered in a Systainer. The Domino assortment contains the following pieces:
- 600 5x30 tenons
- 190 6x40 tenons
- 130 8x40 tenons
- 100 8x50 tenons
- 85 10x50 tenons
- A set of four cutters
Peering into the Systainer full of Domino tenons should get any woodworker's creativity flowing! Here it is:
Now I lay out the milled parts in the orientation I want in the mirror, then set a Domino tenon at each spot that will need a mortise-and-tenon joint. Here are the four parts, with a test Domino at each joint:
Close-up of a test Domino:
To get accurate Domino cuts, all you need to do is hold two parts together you plan to join, then make a pencil mark across both parts where you want the Domino to be centered. As long as you cut both parts oriented to the same line, the Domino will make mortises that align the two pieces perfectly. For this project, these guide lines serve an additional purpose (explained later).
This photo shows the guide lines marked on the wood indicating where I plan to make the Domino mortises:
Preparing the Domino Machine for Cutting
At this point, it is exciting to plunge right in and start making your mortises! But before doing that, there are four simple settings to adjust. All of these adjustments are done with visible, easily accessible dials and controls:
- Install a cutter
- Set the plunge depth (mortise depth)
- Set the fence height
- Set the cut width
Installing a Cutter. There are four cutters available for the Domino. They look similar to small router bits. Here are the sizes (diameter) of the cutters:
- 5mm
- 6mm
- 8mm
- 10mm
For this project, I used the 8mm cutter, which is part of the assortment. It is shown in the photo below (lifted):
To remove or install a Domino cutter, you open the Domino case to gain access to the spindle. The Domino comes with a small wrench that acts as a lever, quickly lifting a switch that opens a lock, causing the motor and fence assemblies to separate. This process is illustrated in the next two photos.
Unlocking the motor and fence assemblies:
Motor and fence assemblies separated:
A close-up of the motor assembly, with a Domino cutter installed:
With the spindle exposed, I loosen the cutter by holding a spindle lock while turning the spindle with the little wrench (the same wrench used to separate the fence and motor assemblies). This process is very similar to installing and removing bits from a router. However, there are two differences: (1) unlike a router bit, the Domino cutter is screwed onto the spindle via a threaded rod; (2) with the Domino, the spindle is tightened or loosened with just one wrench (routers usually need two).
The next two photos offer a view of the method for removing a Domino cutter from the spindle, and a view of the threaded connections:
With the 8mm cutter "screwed on" and tightened, I reconnect the fence and motor assemblies. Two guide poles in the fence assembly line up with the holes in the motor assembly, so you can't go wrong here -- just slide the two parts together until you hear a "click." They are locked and ready for the next step.
Here's a shot of the guide poles in the fence assembly:
And here's the motor and fence assemblies sliding together:
Setting the Plunge Depth. To set the plunge depth, press a clip to unlock the lever, move a green slider to the correct setting (in millimeters), then let go of the clip. For this project, I set the plunge depth to 25mm. That means each member received a mortise a little more than 1" deep (the Domino cuts an extra 1.5mm of depth to allow for glue). The photo below shows the plunge-depth setting:
Setting the Cut Width. Setting the width of the mortise holes is done by turning a green knob to one of three settings, graphically represented with lines of different lengths on the width adjuster. When you are actually cutting a mortise, the Domino cutter swings from side to side as it spins and plunges, thereby cutting a hole of a certain width. The longer the line shown on the adjuster, the wider the cutter swings, and therefore the wider the mortise hole will be.
The mortise width doesn't specifically match the Domino tenon. In other words, no matter which Domino tenon you're using, you can choose any of the mortise widths. Choose the narrowest setting if you want the Domino tenon to fit snugly in the mortise. Choose the middle or widest setting to allow an increasing amount of "wiggle room" when joining pieces later on. Many times, I want to be able to slide the parts around a little bit to adjust them during glue-up, so I choose either the middle or the widest setting. For the mirror project, I did not want any extra space. The Domino tenons had to fit snugly in the mortises, so I chose the smallest width setting.
Setting the Fence Height. If you choose to swing the fence down onto the surface of your stock while cutting the tenons, you need to set the fence height. To do this, unlock the fence, slide it up or down until it lays flat on the surface of the stock you're mortising, then lock the fence. For this project, I chose not to swing the fence down over the stock while cutting, preferring instead to have a clamp in the space usually used by the fence. This will make more sense in a moment, when you see how I cut the mortises.
The photo below shows the fence height (white numbers on left) and cut width (green knob on right) settings:
These settings are a lot simpler than they might seem when reading about them. The first time you use the Domino, perhaps it will take you a few minutes. When I use the Domino, I set the plunge depth, fence height, and mortise width all in about 30 seconds.
Cutting the Tenons
Now I'm ready for the most exciting part of having a Domino machine -- making plunge cuts, creating mortise-and-tenon joints, and fitting the parts together. This mirror project calls for eight mortises: in the ends of each shorter (horizontal) piece, and on the inside edge of each longer (vertical) piece.
I clamp one of the shorter pieces onto my MFT surface with two 120mm clamps. The Domino offers a few different methods for aligning the cutter with your pencil lines. For this project, I chose to use the "pointer" that is molded into the front of the metal fence, which I find precise enough for almost every application I've done with the Domino.
Here's a close-up of the metal pointer:
With the stock held firmly in place, I take a couple of seconds to line up the metal pointer with the pencil line, flip on the power switch, then plunge the Domino cutter all the way into the wood. If you've ever used a biscuit machine, the plunge operation of the Domino will feel very familiar. Throughout the cut, I maintain moderate downward pressure on the handle. When the cut is done, I let the spring-loaded handle return the motor to the starting point, then I hit the power switch. It's all very smooth!
Here's a photo showing the Domino ready to cut an end mortise:
A woodworker's-eye view, sliding the Domino up to an end piece:
The next photo shows the Domino setting up for an edge mortise:
Another woodworker's-eye view, sliding the Domino up to an edge piece:
As mentioned in the previous section, for this project I used the metal pointer to line up my mortise cuts. You also have the option of swinging the fence down onto the stock and using a hairline cursor to line up your cuts. Regardless of the method used to line up your cuts, the plunging operation itself is the same. For illustration, the two photos below show the Domino machine with the fence down, and a woodworker's-eye view of the cursor when using the lowered fence:
In quick succession, I clamp each part down and repeat the above steps. Each time, I make sure the Domino pointer is aligned with the pencil mark I made earlier.
Everything runs along very smoothly -- the Domino never slips or makes a bad cut. The cutter easily plunges into the padauk without hesitation. With the Domino hooked up to my CT22 dust extractor, there is no dust at all throughout the entire mortise-cutting process. This is something I really appreciate, as padauk causes a noxious burning sensation if it gets into your nose.
Cutting all eight mortises took under five minutes (it took me longer to shoot the photos).
By the way, I really like using the MFT as a compliment to the Domino. The MFT provides a great surface for clamping down each piece securely and sliding the Domino machine for each mortise cut.
With all the cuts done, I inspect the mortises. The two photos below show all the mortises cut with the Domino. I did no sanding or clean-up before shooting this photo. You can clearly see how clean all the mortises are:
Using the Domino Mortises as Guides for a 1/8" Grooves
The next thing I need to do is rout the grooves for the mirror glass. As mentioned earlier, I want to use the Domino mortises as a starting and ending point of my cuts. It's time to put the Domino aside for a few minutes and move over to my router table, which has a 1/8" bit installed. Taking two passes, I rout grooves 5/16" deep in each part. This makes the groove deep enough to allow the mirror to shift a small amount.
Below is a view of the 1/8" bit, installed in my router table (another one of my favorite tools, by the way):
Here's where I make double use of my Domino cuts. For each of the long pieces, the space cut out for the Domino mortise serves as a starting point for my 1/8" groove. The Domino mortise is 11/32" wide (Domino thickness) and 7/8" long (Domino width). This allows me to power on the router, then lower the stock onto the table, giving me lots of space to get situated at the start of the cut. Then I push the stock through the cut. When I reach the open area of the mortise on the other end, I lift the stock out of the router.
This photo shows me starting to rout a groove in a long piece, using the Domino mortise as a starting area:
And here's a photo showing me finishing the routed groove in a long piece, using the Domino mortise as an ending area:
For the two shorter (horizontal) pieces, I rout them straight across from end to end.
Now I have two grooves spanning the distance between the mortises in the two longer (vertical) pieces, as show in the photos below:
And I have 1/8" grooves in the two shorter (horizontal) pieces:
Dry Fitting the Parts
It's time for a test fitting of all the parts. I take four 8x50 Domino tenons and insert them into mortises. When the fit is correct, a tenon should fit into the mortises tightly enough to offer some resistance on the face-grain side, but should not be difficult to pull out. With the Domino, I achieve that just-right feel.
The photo below shows how snugly the Dominoes fit:
Things move along quickly from here, as I do a dry fitting of the entire project. First, with a long piece held onto the surface of my MFT (held in place with a set of Clamping Elements), I insert Domino tenons into the mortises, then set the shorter pieces into it. After fitting the first three pieces together, the Dominoes hold tightly enough, even without glue, to allow me to slide in the mirror glass. Then I install the final long piece and inspect the joints. Everything fits together perfectly. Here's a shot of that last piece being placed for a dry fitting (just ignore that guy in the mirror):
Gluing Up and Finishing the Project
All that's left to do now is glue up the Domino tenons and assemble everything for real. Below is a photo of a Domino, with glue on its wide, flat surface. As you can see, there is a generous bonding area:
Using just hand pressure, I pull the Domino joints together most of the way. Mild pressure with a clamp brings the joints completely together. As expected, and desired, there's some squeeze out.
When the glue dries, I trim the edges with my TS55 on the MFT:
For the final steps, I rout a bevel in the edges of the mirror, sand it with the ETS 150/5 sander, then apply the finish. Below is a photo of the mirror, completed but still sitting in my shop:
After adding the hanging hardware, the mirror is placed in my entry area:
There you go. A simple project using the Domino!
Here's a list of items (with links) mentioned in this posting:
- Domino Joiner DF 500 Q
- Cutter & Domino Assortment Systainer
- CT 22 Dust Extractor
- MFT 1080
- 120mm clamps for the MFT
- Clamping Elements for the MFT
- TS 55 EQ Saw
- ETS 150/5 sander
- Woodpecker router table and fence system
Final note:
There is a wide variety of methods you can use to create mortise-and-tenon joints with the Domino. What I have shown here is just one possible set of steps. For a more complete explanation of all the Domino set-up and cutting options, check out these two additional resources:
- "Getting the Most From the Festool Domino Machine" by Jerry Work
- "Enhanced Domino Manual" by Cary Swoveland
Matthew
