Mortise and Tenon Miter Joint?

 This sample languished forgotten in the bottom of my box of Sample CNC cut joinery.  I was sorting out that box and nearly threw it away as it appears to be a simple miter joint.

Looks Simple

Pulling it apart reveals the inner mortise and tenon that hold it together.

Surprise Inside!

The tenon was cut from what is normally cut off to make a miter joint. Mating mortise cut on the other side face. There is no weak cross grain in the tenon. This tenon also keeps the faces aligned when gluing up the miter. While I cut both sides on my CNC, I'm pretty sure this could be duplicated by a clever craftsman without using a CNC. 

Very much the best of two joint types working together to make a strong connection where there is normally a need for added reinforcement. 

With wider boards, each side can have a tenon and a mortise.  Identical cuts using a CNC.  Tenons on each side slide into the mortises on the other side. 

Comments encouraged!

4D 
 

 

Stretching Stretcher

 

Identical halves

Slide together

On occasion I've bumped into the conflict of a solid wood small table top that has grain running 90 degrees from the direction of the stretcher(s) below.  As wood likes to swell or shrink in width as the seasons change the distance between attached end leg frames changes.  In theory any stretcher between would need to grow or shrink in length to accommodate that structural flex. A tenon on each end keeps the stretcher square to the end frame, and a sliding dovetail embrace between the two halves should allow this stretcher to stretch. Tight together in the winter when the humidity drops, and slid open as much as 1/4" when spring arrives and humidity rises. 

This isn't a common problem as experience fabricators know how to orient wood grain to reduce conflicts on assembled wood furniture.  In fact it was only one past student of mine who's design could have benefited from this idea.  That was more than 2 years ago before I retired. I post it here to rid it from my creative mind.   

4D

Wedged Tenon Joint for my Landscape Model Stand Design

Test Sample

My Landscape Model Stand posted here used a wide floating plywood tenon between the feet and the vertical legs. It was never intended to come apart.  This joint is one of a few different prototypes to use as an alternative connection.  It has to be snug with no flex when together, yet not glued so that it can come apart. 

Embedded Square Nut

The mortise was cut 1/16" deeper than the length of the tenon. That allows the screw to pull it in snug and not bottom out. A square 1/4-20 nut was embedded into the bottom of the tenon. The pocket for the nut was cut with a 1/8" spiral end mill. Metal threads being more reliable than threads cut in wood. 

A flat head 1/4-20 bolt pulls the joint tight.

When the wedged sides are pulled together there is no gap or play between the mortise and the tenon. Yet it slides in easily until snug. 

Together tight with no play.

Creating the toolpaths was tedious, and cutting the mortise and tenon sides took considerable time.  I realized after cutting this sample that I do have a 3° tapered end mill. It would have been quicker to draw up toolpaths for and using it would be much faster than using a 1/8" end mill and the fluting toolpath to cut sloped sides of both tenon and mortise. 

3 degree tapered end mill version.

Making the foot out of the same strip of wood as the leg is simpler than making a unique foot from wider material. The design requires a very stiff joint with no flex or wiggle when together.  This wedged joint drawn together with a machine screw satisfies that requirement. Using a stainless steel nut and bolt they won't rust when exposed to the moisture in the wood. I have seen that happen in previous designs of mine. 

Now that I have the details figured out and simplified, I'm making a knock down version of my model stand using Philippian Mahogany.  Light weight yet plenty strong for the application.  2" wide by 3/4" thick legs and feet.  A 3" wide shelf. Stainless steel nut, bolt and hinge at the top. This type of bolt rather then the flat headed bolt used in the test piece above. 

3/8" diameter Aluminum dowels hold the shelf against the legs although if I could find some stainless steel rod or tube already 3" long and 3/8" in diameter I'd use it. 

Test Assembly

A stainless steel hinge recessed flush into their sides holds the legs together at the top. 

Hinged together at the top

With the hinge at the top and the shelf in place the triangle created locks the geometry for a rigid structure. The light weight Philippian mahogany used makes the whole assembly easy to pick up to move about. Slide the shelf off and the legs will fold together for a 1.5" thick flat package that stores easily.  Standing up spread out several of these will nest together.  They can also be stacked, although at 5' tall each the stack would grow in height quickly growing  3" or so with each one added. 

A photo of the assemble design. Note the two black bolts near the bottom of the legs which hold the feet securely.

Stand.  Ing Tall. 

Update 3/1/2025:  The mahogany I used for this stand has some internal stress, and as such the shelf wants to twist and slip back from the legs on one side.  To help it stay in place I bought some rare earth magnets with a hole in the center for a #4 screw. 

Rare Earth Magnet

First to replace the aluminum rods with steel rods. Then screwing a rare earth magnet into the bottom of each hole. That will keep the rods and shelf firmly in place yet allow removing the shelf with a simple tug to overcome the magnetic pull. 

3/8/2025:  Now with some cherry stain and Minwax Polycrylic on it this latest version of my model stand/easel posed for a few pictures:

In summary, the wedged tenon drawn in with a bolt works well.  Of course that joint took my CNC to make, but my CNC is just another tool among many that contribute to the fabrication of my designs. 

Comments welcomed.  

4D  

Woodworking Education: Tiny Table 2

Creative variation opportunities. 

Design students usually strive to be and are encouraged to be unique.   Making the same exact thing as your classmates, just to learn a bit of woodworking, is potentially boring.  With permission to make this final beginning workshop project an expression of their own creativity, a few requirements have to be set so they don't get carried away and miss what they should be learning. 

Tiny Table 2 is simply an aesthetic alternative to Tiny Table 1. Another example for the final beginning workshop project.  All parts differ, but both tables use the same joinery connections between legs and stretchers. Table 2 won't have leg top tenons piercing the top, but instead use one of two standard hardware strategies to attach table tops.  Students are also encouraged to "sign" their work, and the 4DT initials (below) shows one way/place to sign it. Fill the engraved initials with tinted resin then sand flat to the table top. Any scratches that appear in the resin from sanding will disappear once a finish is applied to the top.  

Top Profile

Underside 3D Shape

The stretchers in Table 2 run around from leg to leg rather than cross in the middle.  They attach near the top of the legs, but then have stretchers attached in their middle that cross (half lap) under the table top.  This is where connections to the top are made. These middle stretchers may French dovetail into the side stretchers. When connected to the top they transfer load to the side stretchers.  The legs take the load from the side stretchers to the floor. 

This table is another example of detail continuity throughout the design. The leg profiles visually extend the corner shape of the top down to the floor.  More specific details can be realized and added after the table parts are rough assembled. How the feet meet the floor is one area for consideration. 

Leg cross section.

The outer stretchers have a shallow cove that matches the inward curve of the table top sides.  Bottom and top edges of the outer stretchers are rounded like the underside edge of the top. 

Bottom and Top Edge Curves

Face Contour Matches Top Edge

Even though the assembled dimensions of all tables will be the same, and all will include mortise and tenon joinery, half lap joinery, and potentially more depending on their design, the range of solutions is practically infinite.  Both also demonstrate how to glue up material for their tops, and process the glued up blank down to a finished table top.  The final step for all tables is to sand parts smooth and apply a durable finish. This is best done before assembly but requires taping off any area that is part of the joints between parts.  Then comes glue-up/assembly.  It is the continuity of details that adds to the story you can tell about this table.  That story is what makes the design memorable and desirable.    

Some related educational projects:

Tiny Table 1.

Tiny Table 3.

Tiny Table 4.

Making Samples vs Making Projects

The Joinery Box.  Not About a Box.

The Lathe.

Material Sample Blocks.

Tool Names and Functions.

Determining Actual Project Costs

 

Woodworking Education: Tiny Table 3

Three Legs Under a Triangular Top.

This 3rd example for the final beginning workshop class is to show students both the joinery needed to make it, as well one alternative to 4 legs for this final beginning workshop project.  It is also another example of detail continuity throughout the design. 

The table is made from 4/4 thick (approximately 7/8" actual) face grain white oak.   For the top the oak was ripped into slices 1.125" wide, then tipped 90 degree to be glued up into a 1.125" thick panel. Doing this reveals a more interesting quarter sawn view of the wood grain, and reduces width expansion/contraction by roughly 2/3.  After glue was dry the blank was scraped flat on one side, then sent through the planer (or horizontal drum sander) to clean up.   It ended up 1.0625" thick. The CNC was used to carve the bottom face and cut out the profile.  A trim router with a small 1/8" round over bit around the top edge followed.  

Still fitting within a 9 inch square, the CNC carved bottom face reveals it will connect to a triangular center post.  

Bottom Side.  CNC Carved

Top Side.  Rounded Edge

The center post won't extend down to the floor, but rather just far enough to connect to stretchers extending from 3 legs.   The center post may be made from one solid (or glued up) block using the rotary axis, or 3 pieces mitered together with a void in the middle. 

Center Post Showing Top Tenons.

Tenons cut on the top will match and slip into the mortises cut in the bottom center of the table top.  Three tenons rather than a single center tenon have more glue contact surface area, Spread the load closer to the post perimeter, and have bridges between them to weaken the top less. 

The legs stand on the floor, but don't extend all the way to the top. The leg outer profiles matches the corner shape of the top. Their top edge is notched to match/echo the underside shape at the corners of the top above them. 

Leg 

Inside Mortise

The section view of the stretchers is another opportunity to tie details together in this design.  Rather than with a simple rectangular section, a triangular shaped stretcher could be used.  The tenon shape can also echo the stretcher shape.  Just make sure the mating mortise matches the tenon. 

Triangular Stretcher Option

For some technical variety one could make the center post from 3 mitered pieces. Then use the center void as a wire chase to feed power to an embedded table top wireless charging puck. The wire chase could continue though one stretcher that is glued up from two halves that have a groove running down their middle.  A leg made from two halves could also have a wire chase from the stretcher down to outlet height.  Just make sure the cable is in place when stretcher and leg halves are glued up. 

In summary this project encourages students to think beyond rectangular shapes.  It teaches them how to make more interesting 3D shapes for furniture parts using the technology available.  It opens their minds to think about propagating details throughout a design to aesthetically tie all the parts together.  It lengthens the story that can be told about their design. It is this story of the design details more than a quick glance at it that makes it memorable and desirable.  

Some related educational projects:

Making Sample vs. Making Projects.

Joinery Box.  Not about a box.

The Lathe.

Material Sample Blocks.

Tool Names and Functions.

Tiny Table 1.

Tiny Table 2.

Tiny Table 4.

Calculating Actual Project Costs.

C