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