Housed Tenons Created by Readiris, Copyright IRIS 2005

As an admirer of Greene and Greene furniture, I’ve always been interested in the housed tenon-a joint that was used extensively throughout their furniture, and anecdotally, it appears to have been used exclusively by them. Several folks have told me the Greene’s employed this joint because of the strength it added to joints; and others believe it was employed because it all but guaranteed that, if throughout its life a piece of furniture experienced significant wood movement, a gap would not open between legs and rails, splats, spindles, or crests. It’s easy to say that this additional strength and anti-gap insurance are reasonable features given the prices the Greens were charging. But there are too many others craftsman from this era (i.e.: Charles Rolfs, William Price, Elbert Hubbard etc) who in my mind were just as concerned with the quality and strength characteristics of their furniture who did not use the housed tenon. I wonder why?

Henry Greene Charles Greene

In fact I wondered about a lot of things. I wonder did the Greene’s learn this joint in their training-perhaps at Calvin Milton Woodward’s Manual Training School, which they attended prior to entering MIT’s architecture program. Were they introduced to it from one of the many Asian influences that can be seen in their work? I wonder if they learned of this joint from Swedish craftsman John and Peter Hall; the talented furnituremakers who built their furniture? Minus the answers of where Charles and Henry learned about the housed tenon, I wonder if perhaps its application was to increase efficiency in the Hall’s construction process?

Timber Framing Mortise and Tenon Xray

In the little time I was able to spend researching, here’s what I did learn. The joint appears to have been around for quite some time before the Greene’s starting using it. The majority of the references I found were in discussions of timber framing or timber joinery-thus my thought that the Greene’s learned this joint during their architecture training. Most of the evidence of the joints existence in the Greene’s furniture appears to be after they teamed up with the Halls. So perhaps it was introduced by John and Peter. Finally the xrays I’ve seen of these joints show a loose-fitting and roughly-cut primary mortise and tenon; but a precisely-executed and tight-fitting house tenons. Creating the housed tenon requires the removal of much less material than the primary mortise and tenon. Given the high skill level of the craftsman employed by the Halls, arguably the joint could have been used to save time, or resulted in a more efficient construction process. Eventually I grew tired of searching for answers, and decided to get to the shop and start cutting housed tenons. If you’d like to keep reading about the housed-tenon, here’s some material I found:

The remainder of this post will focus on how to cut a housed mortise and tenon joint in a leg and rail application. As with all of my technique posts, I’ll primarily focus on the process. Mentioning my favorite step-by-step techniques along the way; my hope is that you will create your own step-by-step techniques that make sense for your unique skill-set, tool-inventory, and experience. Housed Tenon Process To begin here’s the process I use for cutting housed-tenons: 1. Cut a traditional mortise 2. Cut a traditional tenon 3. Fit traditional mortise and tenon 4. Shape rail as necessary (i.e.: any shaping that will impact housed mortises size) 5. Lay out the housed mortises with a marking knife 6. Establish the edge of the housed mortise with a chisel 7. Remove mortise waste material 8. Fit the housed mortise and tennon 9. Shorten tenon as required

Step One: Cut a Traditional Mortise

I begin by cutting a traditional mortise and tenon-as if a housed tenon was not to be included. First I’ll cut the mortise. There are an abundance of ways to do this-router, horizontal mortiser, mortising chisels, bench top mortiser, or multi-router to name a few. I routinely use the bench top mortiser, which I’ll show here.

Cutting a mortise and tenon

Because I work almost exclusively with quarter-sawn white oak, I take the time to sharpen the mortise chisel and it’s drill bit before setting up the mortise. It only takes a few minutes and the improved cut quality is worth the investment. A detailed discussion on the setting up the bench top mortiser, including sharpening techniques is found here. One advantage to using the bench top mortiser, is you only need to lay out the start and stop point for the mortises. The bench top mortise fence setup eliminates the necessity for laying out the mortise sides. With the mortiser set up I cut the mortise. I start with a cut in the middle of the mortise and then make over-lapping cuts until I reach the layout lines. Then I go back and cut over-lapping plunges to the other end of the mortise. Finally, I remove the waste and use a chisel and awl to clean up the mortise. Use the chisel for cutting; and the awl for scraping.

Cutting and Cleaning out Mortises I Cutting and Cleaning out Mortises II

As a general practice, when cutting and cleaning out mortises, I focus on not rounding over the edges. But if it happens here, remember this edge will be removed later in the process when we cut the house-tenon mostise.

Step Two: Cut a Traidtional Tennon

As with step 1, cutting the mortise, the housed tenon is not considered in this step. We’re just going to cut a traditional ternon. The only exception to that statement is regardless of the tenon width, we’ll make no adjust for wood movement-aiming for a tight fitting joint to provide a rail that won’t move when we trace out the housed-tenon mortise. As with any woodworking operations there are multiple ways to execute it. I prefer to use my tablesaw and a dado set to cut tenons. This allows me to sneak up on the final tenon thickness. Then with a few shavings from a shoulder plane or patternmakers float, I can finalize the fit.

Step Three: Fit the Traditional Mortise and Tenon

As mentioned in the previous step I’ll sneak up on a tenons initial thickness. I plan my initial tenon off the tablesaw to be slightly too thick. Then I’ll identify a reference face and an adjustment face for each pair of rail tenons. Normally I’ll designate the face that is orientated outward on a table or cabinet as the reference face. I’ll mark this with an “R” and make all adjustments to the opposite tenon face. When fitting a tennon I’ll adjust, in this order:

Fitting Mortise and Tenon

  • Tenon thickness-by taking material off a face
  • Clean up the mortise bottom
  • Bevel the tenon ends
  • Bevel the tenon shoulders

I’ll test the fit after each adjustment. Because each step slightly reduces the glue surface, When I have a perfect fit , I’ll stop progressing through these steps. It’s good to be thinking ahead, because the faces of the rail will be your template for laying out the housed-tenon mortise. A sloppy fitting joint will result in a sloppily laided out mortise. Remember our goal, is to have a very tight fitting housed-tennon, that is not visible to the casual observer.

Step Four: Shape the Rail (as necessary)

If the rail requires shaping, I’ll do it now after the tenon fitting is complete, and before laying out the housed-tenon mortise.

Step Five: Lay out the Housed Mortise with a Marking Knife

Begin by dry fitting your mortise and tenon. The faces and edges of the rails will be your lay-out guide for the housed-tenon mortise.

Dry Fitting Mortise and Tenon

Begin by lightly tracing the edges with a sharpe marking knife-I’m currently using a Czeck Edge Hand Tool, which I find very good for this purpose. The first light pass should be just enough pressure to cut the wood fibers and establish the line. Start the cut against the edge and end just past the intersection of the rails edge and face. Then take a second pass with increased pressure to add a bit more depth to the line. Next use the same two-cut approach on the rail faces. But be aware that most cutting knifes, when dealing with a 2″ or wider rail will not register flatly against the rail fence, and will have to be tilted away from the face to allow a trace of the full face. This will actually result in an outline that this is slightly thinner that the rail is thick, depending on how much your marking knife required to be tilted.

Step Six: Establish the Edge of the Housed Mortise with a Chisel

Edge Around Mortise

In this step I’ll establish an edge around the mortise, its purpose is to provide a shoulder to register the chisel back as we continue to remove waste, trim the edge, and fit the tenon. Remember this edge is going to show in the finished joint so be careful to leave a nice crisp edge. I produce this edge by gently removing a chip of wood, from the waste side of the mortise; using the marking knife line as a stop for the edge. After taking out a small chip around the perimeter of the mortise I use the slight edge established, along with a good flat-bottom chisel and make another reference cut around the mortise. Then remove a larger chip to reinforce the size and strength of the mortise edge.

Reinforce Size and Strength of Mortise

Step Seven: Remove Mortise Waste Material

With the edge of the mortise established and able to support chisel work, I’m ready to remove the waste from the mortise. I do this using a Dremel rotary tool mounted in a Plexiglas plunge base. But first, I draw a pencil line on the edge I created in step six. It helps contrast the edge and allows me to see it better when viewed through the Dremel’s plexiglass base.The Dremel, with an 1/8″ straight bit installed, is stout enough, and powerful enough to remove waste from oak, yet not so powerful that the operator loses control of the tool. The Plexiglas base makes it possible to see through the base and monitor the cut in progress. The combination of the Dremel and clear plunge base make it possible to quickly remove the waste AND be in total control of the operation without needing fences or jigs to control the router.

Removing the waste from the mortise Rotary tool

Next, using a router plane, I’ll clean up the mortise. While the Dremel and straight bit leave a sufficiently smooth bottom, cleaning up with a router plane does a nice job of smoothing the bottom, but it really earns its reputation by cleaning up the corners formed by the sides and bottom of the mortise.

Router plane IRouter plane II

Step Eight: Fit the Housed Mortise and Tennon

Now it’s time for our initial joint fitting. More so than with other joints, you must be very careful fitting this joint. Because if you damage the sharp corners at the top rim of the mortise it will show. Remember there’s no rail or stretcher shoulder covering the mortise–so be gentle when you fit the joint. If necessary relief the corners of the shoulders on the tenon board. This will help you ease the rail into place.

Fitting housed mortise and tenon I Fitting Housed Mortise and Tenon II

Remember, back in step 1 and 2 you made a traditional mortise and tennon? Well, now that you’ve cut a housed-mortise the joint won’t completely seat because more than likely the tenon is bottoming out in the traditional mortise. In fact, if you precisely executed each step, your tenon should be too long, by a distance equal to the depth of the hosed-mortise; and the joint won’t seat completely until you’ve completed step nine.

Step Nine: Shorten Tenon as Required

Begin this step by shortening the tenon by the amount that the house-tenon mortise is deep. This step is necessary because with this joint, you’re fitting the tennon and its shoulder into the mortise, and you won’t be able to see if the joint has seated completely. One way to confirm a proper fit is to listen for the tone change as you lightly tap the joint closed with an assembly mallet. Another is to draw a light pencil line on the tennoned board shoulder when you think you’ve got the joint closed. Then pull the joint a-part. If the joint was closed properly the distance from the pencil line to the edge will be equal to the housed- mortise depth.

Shortening the tenon I Shortening the Tenon II

It sounds like a lot of steps and a lot of work, but it only adds a little bit of time to your traditional mortise and tenon cutting time. So why not create a piece of furniture using joints that will truly pass the test of time!

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