Small table and a white pipe.

In an effort to use up materials I've collected over the years, this project employed a section of white painted pipe as the structural post of a small table. The table top I made awhile back as a challenge to use up scraps of short lengths of wood.  Scraps ripped and tipped and glued together to make a roughly 10" x 10" panel, then CNC cut into an interesting shape and bottom contour. 

The top needed some structure to hold it horizontally above the floor.  18 to 24 inches tall was the desired height I wanted the table to be. I have at least 3 identical section of white pipe.  One pipe alone made for a simple design.  I just needed to come up with a structural way to connect it to the top and a base that spreads out the load so the table wouldn't easily tip over. 

Connecting wood to metal pipe was the challenge. I deformed the end of the pipe to a shape that wouldn't spin in a pocket.  I chose a hexagon for the end cross section.  I had to CNC cut a negative form to press the pipe into using my bench vise.  

Round to Hex over 2 inches

1" thick HDPE I have on hand, so I cut forms from it. High density was the desired quality.  I didn't want a form that the steel would deform before the form could reshape the steel.  

HDPE worked.  

With a way to reshape the pipe ends, making a pocket for the hex ends came next. To hold the pipe between table top and base I ran a length of 1/4-20 all-thread through the pipe. I used a cap nut on the top and a nylock nut on the bottom end.  The bottom nut will be under the base and not seen.  The top cap nut is decorative, flush, and in the center of the top. The pipe runs straight up from base to top.   

It took two tries to cut a pocket that the ends of the pipe would slide into.  I checked the fit while the board was still on my CNC.  Simply enlarged the vectors used, recalculated the toolpaths and cut again. I had a 1 degree taper on the sides of the hex hole, and although the pipe can be drawn in I fear the board may split.  I replaced the initial block making a new one with a simple pocket with straight sides. 

A simple base design came next.

The wood block has a board on each side. The boards extend to be the feet of the table.  The boards half-lap/interlock to surround the center block. 

Base slat with slots

I designed a wedging half lap joint cut with a CNC, and used it in assembling the 4 base boards.  A spline in two sides of the block and two of the surrounding wood slats will structurally keep it in place. Glue will do the rest. 

 

Base slat edge refined

To refine the edges of the base boards I drew a curve that when intersection each board would a 3 degrees from horizontal.  Knowing I had a 3 degree tapered router bit I then cut the curves using that bit. Look close at the base of the table in this photo and you'll see the crisscross pattern curves all blend together. 

Now that all parts are made and assembly is verified, It is time to put some stain and top finish on the base boards and the table top.

I'll add a photo here when I have the table stained and finished.

Comments and questions always welcomed,

4D

Tapered Radial Finger Joint

Tapered fingers

Mating side

Advantages: 

- The two halves slip together easily. 

- They fit tight when fully together. 

- When assembled they have a unique look.

- Mating surface don't touch until fully together.  No scraping off glue when assembling.  

Renders above are from my CNC software. 

This joint was not easy to create the toolpaths for.  It took drafting skills I learned in high school and the great drawing tools in my CNC software to create.  Tips of the fingers are the same width as the valley between them. One half fills the center area left by the other half.    The tapered sides were accomplished with a 3 degree tapered end mill.  It has a 0.125" diameter tip, 3 degree tapered sides, and just a little over 1" of cutting depth. 

I'll use this joint for top and bottom zebra wood caps on 1.5" diameter cherry dowel legs. Applications are anywhere you want to join round wood parts end grain to end grain. Only limited by your ability to clamp parts vertically within your CNC cutting limits. If you do use this joint please consider referring those who see it back to this post.  

With straight cut finger joints there is always a conflict of fit. A battle of wit. Too tight and the fingers may not fit together at all. A perfect match and while they do fit together they are a challenge to assemble and any glue in the joint gets scraped away when you do assemble them.  Make the joint looser and you have a loose fit that glue ends up filling across gaps. By CNC cutting with 0.001" accuracy the fit of these tapered joints is both easy to apply glue to and assemble, and will go together tightly with even contact between inner surfaces.

3 degree taper between fingers. 

Test cut example. It is critical to center the toolpaths for each side of the joint. Check back for final project images. 

Comments are encouraged and welcomed.

4D