Introduction: Truncated Icosahedron Kumiko Lamp

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About: Hi, I'm Brian. My goal is to make fine woodworking — and especially Japanese kumiko woodworking — accessible and fun.

This lamp is something I've had on my mind for a while. I'm going to be honest: It's not for the faint of heart. But if you have experience with kumiko — or are just really bold — I think you could do it.

Supplies

Step 1: Mill the Lumber

The first step is to mill your lumber to 1/2" by 1/8" strips. I do this by planing my 1" basswood lumber to 1/2", then cutting that board into thin strips between the table saw blade and the fence. I actually have another Instructable on this very process, so I won't go too in-depth here. Once you have your strips, you can move on.

If you're using the 1/8" pre-milled basswood strips, you can skip ahead to Step 2.

Step 2: Cut the Crosslaps

For this project, we need 20 hexagons, which means 420 crosslaps in all. There's actually two types: tall and short. The tall are cut about 2/3 of the way through the piece and are cut on both fences, which makes this point in the thickness of the strip that you can see in the image. The short laps are cut 1/3 of the way through, then flipped to cut 1/3 on the other side of the strip. In all, cut 280 tall laps and 140 short laps.

I also have an Instructable on building this hexagonal kumiko sled if you want to know more about it.

Step 3: Make the Hexagonal Kumiko Grids

The way these grids fit together is pretty cool. You will need:

  • 2x type A with 3 notches
  • 1x type B with 3 notches
  • 4x type A with 2 notches
  • 2x type B with 2 notches

(image 1)

First, take one three-lap type A piece and put glue into the laps.

Then, take the three-lap type B piece and connect the center with the center lap on A to make an X shape. (image 2)

Afterward, attach the two-lap type B pieces to the type A strip, making this sort of backwards uppercase N shape (image 3).

The whole thing gets locked together with the second three-lap type A strip, which forms two triangles that point to each other. (image 4)

From there, just attach the two-lap type A pieces on the outsides, then flip and add the last two two-lap type A pieces. (images 5 and 6)

Finally, once the glue has dried, cut the excess away with a hand saw.

Step 4: Make the Kumiko Patterns

I would recommend using the basic Asanoha pattern. It's striking, but only requires bevels on the ends of the pattern pieces and nothing more. There are 360 individual pattern pieces, so choosing a pattern that is complex could mean a lot of extra work.

Cut all 360 individual pattern pieces slightly oversized.

Bevel the 30 degree ends

Using the 30 degree side of a 30-60 kumiko jig, bevel a 30 degree angle on each side of one end of the infill pieces. This is easily done with a chisel or one-handed plane.

Bevel the 60 degree ends

Now's the critical part. You want all three of these infill pieces to meet at the exact center of the triangle. This means they all need to be the exact same length, with 60 degree bevels on each side.

The easy way to do this is to sneak up on the fit, intentionally taking less than you think you need until you get a nice friction fit. Once you get the dimension for one triangle, you can lock the settings and bang out the rest.

Glue the patterns

It's not entirely traditional to glue the patterns, but it really helps with structural rigidity, so I'd recommend it. Normal wood glue works here.

Step 5: Bevel the Dihedral Angles

Dihedral angles is a fancy term for the angles at which the hexagons meet. This is a truncated icosahedron, which has 12 pentagonal faces and 20 hexagonal faces. It also has specific angles the faces must adhere to. For the lamp, I’m really only going to need the hexagon-to-hexagon meeting angle, which is 138 degrees.

To get this angle, you need to cut bevels on the outside of the patterns — on 3 faces per pattern, to be exact. The easiest way to do this is with a table saw jig. I whipped up a quick one using MDF and some stop blocks, before setting the table saw to 69 degrees (half of 138 degrees) and making cuts. Check out the last picture to see the angle these bevels allow.

Step 6: Glue the Panels Together

This is, by far, the most difficult part of the project. You need to glue these hexagons together. I used CA glue for a quick bond, wood glue for a permanent bond, and then a spring clamp to hold the panels together while gluing.

Just take your time with this.

One thing that really helped me was to import a truncated icosahedron into Sketchup so I could move it around and look at the faces. I'd recommend that or something similar so you can see what you're looking to achieve.

Note: if you're going to paper the panels, look ahead to the next step. You won't be able to attach paper with the polyhedron assembled.

Step 7: (Optional) Paper the Panels

If you're going to put paper behind the panels, do it before the panels are all assembled. I stopped when I had these four-panel shapes (images 1 and 3), and they were very easy to apply paper to.

I simply used handmade mulberry paper and some 3M Super 77 spray adhesive and had no trouble papering the panels.

Once done, assemble the rest of the lamp shade.

Note: the pentagon shapes were quite difficult to paper over and it had to be done with the shade fully assembled. Consider adding no paper to the pentagon areas if you're not comfortable with this.

Step 8: Light It Up

Using any lamp base of your choice, install the lamp shade over it and stand back to admire your work. The lamp base I used was from an older Menu lamp, but pretty much anything that has a relatively narrow and short bulb socket should work.