Secret Tenon Finger Joint

Wanting to make functional, but attractive pieces that I could use in my own home, I though what better a joint than a corner joint that looks seamless, but is incredibly strong.

Then I found the secret tenon finger joint, which looks like this:

It has the obvious CNC design, with little mouse ears around all the interior corners, but because of the way it goes together you’ll only see them, and only just, on the interior corners.  The exterior corners look great, with only a small piece of end grain showing on the very edge.

I recreated the joint in Vectorworks and went right to the CNC.  I found that adding notes to myself in Vectorworks is extremely useful, since I can just ignore it in CAM, I can comment to my heart’s content.  One note, I didn’t have the recessed lip on the first drawing.  That was an oversight and it became apparent as soon as I put the joint together.

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Round 2 – I added in the recessed lip.

Round 3 – increased the depth of the lip to try and get the parts to fit a bit more flush.

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All of em together:

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The joints were still super tight, even after opening up one side by about 0.1″.  But I don’t mind that they’re tight.  It just means I can be confident in their structural integrity. I think…

2 thoughts on “Secret Tenon Finger Joint

  1. Ben Light

    Nice work. I’m so glad you made multiple iterations.
    Great idea to comment your drawings and mark up your plywood samples.
    You’re almost there, I think if you made one more, just a bit tighter, you’ll have what you want.

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