This variation of the mortise and tenon joint is the perfect choice for traditional frame and panel doors.
When it comes to building strong frame and panel doors for a cabinet or other piece of furniture, you have several joinery choices. Often, I’ll use stub tenon and groove joinery. It’s simple, quick, and results in a fairly strong door.
But if I’m building a traditional piece of furniture with frame and panel doors that feature solid wood panels, there’s another joint that I prefer to use, and that’s the haunched mortise and tenon. And here’s why.
PLYWOOD PANELS.
If you’re building a door with a plywood panel, you don’t have to worry about expansion and contraction of the panel inside the door frame, so you can glue the panel into the frame. The glued-in panel adds strength to the door. In this case, a stub tenon and groove joint is plenty strong, because once the panel is glued into the frame, you end up with a single, rigid assembly.
SOLID WOOD PANELS.
On the other hand, a solid wood panel shouldn’t be glued into its frame because it needs to have the freedom to expand and contract with seasonal changes in humidity. Since the panel merely “floats” in the frame, all the strength for the door has to come from the joinery used to build the frame.
Now, in terms of strength, it’s hard to beat a mortise and tenon joint. The haunched mortise and tenon is simply a variation on that joint. It has all the strength of a traditional mortise and tenon joint, along with an added bonus.
The advantage is the “haunch” or short stepped shoulder on one edge of the tenon. As the door rails and stiles are assembled, the haunch fills in the end of the groove that holds the door panel, as you can see in the drawing above.
This haunch allows you to cut the grooves along the entire length of the rails and stiles, instead of having to make stopped grooves or glue plugs into the open ends of the groove. In addition, it provides more lateral stiffness to the construction of the door.
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| Haunched mortise and tenon joints are a good choice for solid wood frame and panel doors. |
MAKING THE JOINT
If you take a look at the box on the opposite page you’ll see that the process for making a haunched mortise and tenon joint is a lot like making a traditional mortise and tenon. There’s just one extra step to add and that’s making the centered groove for the door panel. I like to cut these grooves in the frame pieces as the first step. The reason for this is that the walls of the groove will help you gauge the width and location of the mortise.
MORTISE FIRST.
There’s nothing out of the ordinary when it comes to the mortise. I simply drill out the waste using a Forstner bit on my drill press. The nice thing here is you can use the groove in one of the door frame pieces to help position the fence on your drill press.
After drilling the holes, you can square up the mortise with a chisel. Here again, the side walls of the groove help guide the chisel and keep it straight and square.
NEXT, THE TENON.
Once the mortise is complete, you can cut the tenon to match. And I think you’ll find that the groove will come in handy in the setup, as well.
Simply lay one of the door frame pieces on the table saw and adjust the height of the dado blade so the tips of the teeth are flush with the lower edge of the groove. Then you can cut both faces of the tenon by making multiple cuts with the dado blade, as shown below. (For a more detailed discussing on cutting tenons on a table saw, see the article on page 38.)
MAKING THE HAUNCH.
After cutting the tenon cheeks, you’ll cut away the waste on the edge of the tenon. And here’s where the haunch comes into play. To create the haunch, you simply leave the shoulder a little longer by not trimming the waste all the way back.
There’s just one other thing to note here. Ideally, the length of the haunch should match the depth of the groove. But I like to cut the haunch just a hair short. (I’m only talking about 1⁄64" or so.)
The reason for this is simply to prevent the haunch from bottoming out in the groove before the long shoulders of the tenon seat against the edges of the mortised piece, as shown in the drawing above. This ensures a tight-fitting jointline where the pieces meet.
While it may seem like a small detail, haunched mortise and tenon joints are one of those things that make the difference between run-of-the-mill construction and a special project that really stands out. And the best part is they aren’t really difficult to make.
How-To: Make a Haunched Mortise & Tenon
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| Cut Grooves. With a dado blade on your saw, cut a centered groove along the edge of each frame piece to hold the panel. | Set Drill Bit Depth. Adjust the depth stop on your drill press to regulate the depth of the mortise. Then drill out the waste. | Set Saw Blade Height. Using the shoulder of the groove as a guide, raise the saw blade to cut the tenon shoulders. |
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| Establish Shoulder. Now cut the shoulder on one side of the tenon first, using the rip fence as a stop. | Remove Waste. Remove the rest of the waste by making multiple passes. Then repeat the process for the other cheek. | Create Haunch. Trim the waste on the edge of the tenon, leaving a haunch that will fill in the groove on the mating piece. |
