CNC cut Hardwood Dowel Joinery

My first job out of college was for a furniture company noted for the metal framed residential furniture they made and sold. It was all designed to quick assemble.  No welding of metal parts. Clever engineering of steel connections made their furniture go together rigid and precise. One connection they used between small tubing into larger tubing was to taper the end of the small tube, then pull it tight into a slightly smaller die-punched hole.  This post is about a wood version of that connection.  

For this sample a three degree tapered end mill, a 3/8" diameter wood dowel, and a 1" diameter wood dowel are used. 

Taper the dowel and the hole

A 90 degree connection that wedges tight and stiff with no glue.  Draw tight with a wood screw. 

Pocket hole screw

Clean, precise, and easy to create.

The small dowel end was pre-drilled for the pocket hole screw. 

Pre-drilled for screw threads

Trapped tight in the tapered hole there is no chance the small dowel would split. The counterbored hole for the screw head could be covered with a wood plug. For a coffee table or end table a frame made from dowels using this joint could have the side frame pre-assemble and only require the end stretcher dowels to be screwed into the legs.  A simple wood frame that is rigid with clean joinery and no glue required. Hardwood dowels are available in many species. Imagine a tempered glass top resting on the frame to finish it off. 

Comments welcome!

4D

  

Whimsy in Design. Magnetic Appeal.

Whimsy

I started with a small table top made for a rejected project.  I added in a couple of 36" long 3/8" diameter dowel rods I've had for a couple decades or more. I cut them in half to be the legs.  Then I made 4 wood balls.  I mixed in some 3/8" diameter magnets left over from a previous project, and this is the result. 

I drilled holes for the dowel legs in the bottom of the table top using my CNC.  I wanted the dowels to angle out rather than stand straight up, so the CNC jig was tilted 5.8 degrees down from horizontal. 

On my Compound Angle Clamping Jig 

Rather than glue the dowels in, I embedded magnets into the bottom of the CNC drilled holes.  Since wood won't stick to a magnet, I inserted metal screws into the ends of the dowels. The biggest challenge was centering the screw heads on the dowel ends. A bit of filing might have happened to make them slip easily into the holes. 

Embedded Magnet

The holes in the top were limited in depth by the screws that held the magnets in place. Any deeper and the screws would have poked out the top.  An ideal design would have deeper holes to better brace the inserted dowels. 

For feet I made wood balls, 1.5" in diameter.  They need a 3/8" diameter hole in them.  They will get magnets in the bottom of the holes and as such also stick to the screws in the ends of the dowels.  For whimsy I'll painted one of them red.  Experience tells me the one red shoe will make the table more memorable.  

I gave my CNC rotary axis a chance to prove it could make wood balls.  

Five Maple Balls on my Rotary Axis

Five 3/8" Diameter Holes

One Ball, ready to trim. 

Four wood ball feet.  Ready for magnets and a finish.

Rare earth magnets hold all the parts of this table together.  You could replace the wood dowels with steel rods and skip having to add screw heads to the end of the dowels.  That would add considerable weight, sterilize the composition, and require paint to prevent the metal from rusting.  The wood dowels are just enough.  No more than needed to hold up the top. When whimsy strikes you can pop off the ball feet and replace them with perhaps a seasonal color alternative.  How about 3D printed shoes to slip over and magnetically stick to the dowel ends?

 

All projects survive longest if the parts have some finish on them.  I set about first applying clear finish to the wood balls.  No problem with the first three, but the 4th ball protested.  It tried to escape by rolling off the bench, but I caught it. It got so angry at the thought of joining the clear finish crowd that it turned red in the face.  In the end it got its way.  Meet the angry red shoe.  I may have to rename this post as "A Table with One Angry Red Shoe.  

One angry red foot.

The ball feet balance the composition.  An echo of the thick top. They recognize the thin dowels as official table legs. Although this little table stands up proudly, the thin dowel legs happily flex a bit, and a bump against the table top will reward you with a quick wobble dance. Not a table you'll want to sit on. Not a table for anything like a small TV.  Park the TV remote and maybe a coaster with a drink on the top. A frail little table such as this one needs a place out-of-the-way.  Where no one might accidently bump it.  Not in the open where predatory beasts in the house might find it. A more stout version with thicker and stiffer legs would eliminate the wobble, but also remove the joy the table elicits when it does dance a bit.  😉

Comments welcomed and appreciated.

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