Impossible Joint (Osaka Castle-Otemon Gate's Pillar Splice)




Introduction: Impossible Joint (Osaka Castle-Otemon Gate's Pillar Splice)

Otemon gate is the only known example of this design. No gap exists between the two pieces.

To make this decorative but very strong joint you will need:

  • (2x) wood pieces 15.0 x 7.0 x 7.0 cm
  • Hand saw
  • Chisel (14 mm)
  • Hammer
  • Sandpaper 120 and 240 grits

A quick video of it:

Step 1: Male Part Marking

Firstly make sure you print the plans I provide and scale them up or down if your wood pieces are different in dimensions than mine.

Mark out all the sides of the wood piece according to the plans.

Step 2: Cut the Male Part

Use a hand saw to cut the male part. With a chisel finish and clean up if necessary. Make sure you stay outside the lines so you have the space to work with your chisel.

Step 3: Mark the Female Part

Again mark the female part according to the plans. For a better fit you can always measure the male part and mark the female accordingly. This will eliminate any misalignment between the male and female part.

Step 4: Cut the Female Part

Again with your hand saw carefully cut just a tiny bit inside the lines. Then clean up with your chisel.

Step 5: Finished!

For this project I used two pieces of pine. In order to make a better contrast between the two part I used a brown wood dye on the female part.

To assemble the two pieces just push diagonally the female part on the male part. Make sure you have a tight fit and adjust with your chisel if needed.

You can always check here for more info on Japanese Joints.



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    7 Discussions

    WOW! Beautiful joint, seriously clean and yet elegant.

    The PDF manual looks to be phenomenal. Thank you for including that.

    Wow that is an incredible bit of workman ship. Thanks for sharing!

    are the dashed lines in the PDFs intended to be perpendicular to the lines they connect? For example, in Male Part B view, the dashed lines at the top are 2.5 cm from the left edge at the top, and assuming that tapered dovetail is centered, the dimension of 2 cm where the taper meets the outside wall indicates that the dashed lines should be perpendicular to the horizontal lines. They are not shown this way in the drawings, but I am wondering if that is the intention.

    Thanks, and the joint looks great.

    1 reply

    Please check the last step. You will find a link to a pdf. The very well made plans are in there. Different dimensions though but you can scale them up or down.
    If you have any more questions please let me know. I will redraw the plans if needed

    I was expecting boiling, compressing, breaking/gluing, but not actually a real joint! Great job on making a real impossible looking joint actually possible!

    1 reply

    Thanks a lot my friend. The first time I saw it I thought exactly the same. Once you mark the oieces precisely then it is quite easy.