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Kumiko Inlay Serving Tray: Description and Build Notes

A Maple Serving Tray with Kumiko Inlay and Cherry Accents

This project was my variation on a project I saw on a YouTube video by Pask Makes (Niel Paskin). He made a large table. This was way too big for my needs, so I scaled it down to a serving tray, and tweaked the design and process to suit my needs.

The basic idea was to glue a lot of 120-30-30 triangles to a base board in a Kumiko pattern, and then fill the gaps with black epoxy.

The first step was to mill some maple boards to make them a bit thinner, about 0.60 to 0.65 inches rather than 0.75. I then ripped these boards to make a lot of 1/8” strips. I found the DRO on my table saw to be really good for this. I used incremental mode, and after every cut, I would zero the DRO and move it 0.250 inches. With a 1/8” kerf, that gave me 1/8” thick strips.

Lots of Wooden Strips

Then I needed to cut these strips into triangles. This is one place where I diverged from the original video. I didn’t like the idea of registering the triangles on the sharp point. I thought it was a better idea to register on the flat side of the triangle, and to keep the strip contained during the cut. So I made a simple jig for the table saw that just had a long fence at a 30° angle, and then a shorter stop at 30° to the fence. The location of the stop fixed the length of the triangles. I was shooting for a 2” long side, to roughly match the scale of my earlier Kumiko work.

Triangle Jig

I held the strips against the long fence, and I held the cut-offs (e.g. the triangles) with a pencil eraser. The triangles were much too small to try to hold the triangles with my fingers. That would get my hand way too close to the blade.

Holding Cut-Offs with Pencil Eraser
Making First Cut at End of Strip
About to Complete a Triangle
Triangle Completed

After cutting about 600 triangles, it was time for a small scale test. I was concerned with getting bubbles in the epoxy, so I first tried some stuff designed to minimize bubbles. It was very thin and took a long time to cure. It took several days to start to harden and a week before I could work it.

Filling the gaps makes a mess of the top, so after the epoxy step, it looks really ugly. The idea is to sand off the top layer and be left with the wood and epoxy just in the gaps. I proceeded to do this, but I found that the top of the triangles was covered with black lines. I kept sanding and sanding, which was apparently going really slowly, until the pattern just became a big blobby mess. At that point, I realized that I had sanded through the entire 1/8” thickness of the triangles. In other words, those black lines were not on the surface of the triangles. They were all throughout the inside of the triangles! I think that the epoxy traveled up the pores or vessels within the wood, and so were throughout the whole volume of wood.

First Failed Test
Triagles Sanded Through

I think that Mr. Paskin may have lucked out in his table project. Originally, he had decided to fill the gaps with clear epoxy, but after pouring it, he decided that he didn’t like the way it looked. Somehow, he either removed the clear epoxy and replaced it with black epoxy, or introduced black coloring into the clear epoxy. I’m guessing that perhaps the clear epoxy filled the pores accidentally, and thus the black epoxy didn’t travel up them.

This would be the start of a long series of tests.

I figured that the black lines were occurring because the epoxy was so thin and took so long to set, so I got some “normal” epoxy and tried again. This cured much faster (overnight), but I still got the black lines.

I tried to seal the edges with glue, as I was gluing the triangles down, but that didn’t work either.

By the end, I had made six trials before I found a way that would work.

Six Trials

Eventually, I tried the approach that I was dreading, but which finally worked. This was to seal the ends with shellac. The reason I was dreading this approach was that it added a significant amount of time and effort to the project. I wanted a good seal, and I wouldn’t know if I had one until the project was essentially finished and I applied the epoxy, so to be safe, I used two coats. I applied the shellac to one face and all of the edges. I’m not sure if I needed to shellac the face or not, but I figured it was better safe than sorry, and it didn’t take appreciably longer.

Final Test

Then after the shellac had dried, I lightly sanded the face without the shellac. This was to remove any shellac that had gotten onto that face, and to flatten the face. I didn’t want burrs, splinters, or bits of shellac to keep the triangle of seating properly on the base, and perhaps compromising the glue joint.

The shellacing and sanding added a number of hours to the project. Each triangle didn’t take too long to process, but when I had to do hundreds of them, the time added up.

It was then time to start gluing the triangles onto the base board. I thought of the design as consisting of a number of rows. Within each row, three wooden triangles formed a big triangle, and then this big triangle alternated pointing up or down along the row.

There were two things that I wanted to control, but I could only control one of them. I wanted a 1/8” gap between triangles, and I wanted the “columns” to line up. In an ideal world, both of these would be satisfied at the same time, but in the real world, if I adjusted all of the gaps to 1/8”, then by the end of the row, the accumulated errors in gap size would cause the triangles in a column to not quite line up. On the other hand, I could line up the columns, but then the gaps wouldn’t all be quite the same.

I decided that it was more important that the columns line up, and that minor errors in the gap thickness would not be too noticeable. So I drew a set of parallel lines from the top to bottom of the base board. The spacing between the lines was exactly half the spacing of the large triangles. This may become clearer shortly.

For the first row, I set up two straight edges to serve as the bases of the large triangles. For subsequent rows, I only used one straight edge, with the other edge being set by the previous row.

Two Straight Edges for First Row

Ideally, I would glue down each triangle and clamp it in some manner (perhaps with a weight), but I couldn’t think of any reasonable way to do this. In the end, I just held them in place and applied pressure with my fingers for a short while before moving on. I used Titebond II, as it had a fairly quick working time.

I cut some strips of wood to 1/8” thickness, and then cut them into squares to use a spacers. I tried waxing them to try to keep the glue from sticking to them. This may or may not have helped.

I glued one large triangle at a time. First I would glue the base wooden triangle down, with its base either against the straight-edge, or against spacers against the previous row. I would align it so that the apex of the wooden triangle lined up with one of my drawn parallel lines. Then I would glue in the other two wooden triangles at the same time. I used three spacers to control the gap between wooden triangles, and I aligned them so that the drawn line was down the middle of the gap between the two new triangles.

First Large Triangle Glued with Spacers
In the Middle of a Row

This left the gap between big triangles “uncontrolled”, but if I had the width of the row set correctly and the line spacing correct, then the gap between the big triangles should be pretty close to 1/8” as well.

First Row Completed
Partway Through Second Row
Half Done
Flipped To Work on Second Half

I found that it took me about an hour to glue in one row. Since there were five rows, the basic gluing took about five hours. Originally, I was going to go with six rows, so that it would be symmetric, but then I decided that this would make the tray a bit too deep, so I stopped after five rows.

At the end of the rows, there were a number of half triangles that I needed to glue in. In theory, I could have taken a wooden triangle, cut it in half along the center with a 1/8” kerf, and gotten two ideal smaller triangles. In practice, I located a wooden triangle into each spot, marked a line where the cut should be made, and then custom cut each one. It was too scary to try to cut something like that on the table saw, so I ended up using an old manual miter box saw that I had bought decades ago before I had a table saw. Of course, after cutting them, I had to shellac them before gluing them in.

Sawing the Half Triangles
About to Glue in Half-Triangles
Just Finished Corner Half-Triangle
Done With Triangles

For the edges, I got some 1/8” cherry and cut it into 1” wide strips. I mitered the corners and cut them to a length that would give me a 1/8” gap around the outside. When I glued these strips down, I did use clamps.

With Cherry Edge Glued On

Then it was time for the epoxy. I had learned from my small-scale tests that while the epoxy was somewhat viscous, and the channels were fairly small, it would flow before setting up. To counteract this, I carefully leveled the board (using playing card shims) before applying the epoxy.

After the epoxy had cured, it looked like a horrible mess. After a lot of sanding, it cleaned up nicely.

After Applying Epoxy
After Initial Sanding

However, I noticed a number of bubbles that had been exposed by the sanding. I mixed up some more epoxy, and applied little dots to each hole with the tip of a toothpick. After that cured, I sanded it again.

After Final Sanding

I figured that it would be easier to finish the bottom before it was installed into the serving tray, so I proceeded to apply several coats of polyurethane to both side of the base.

After Applying Polyurethane

With the base finished, it was time to start on the sides of the tray table. These would be comparatively simple: four sides connected with box joints, with a stopped groove in the bottom to receive the base.

I drew out the curves I wanted for the ends with the handle and made a template. I traced those curves onto some quarter inch maple, then cut just proud of the lines. I attached the template to the real wood and pattern routed the curves. I did a little rounding around the handle and sanded the edges and inside.

Rough-cut End

To make the box joint, I ended up using a box-joint jig that I had built many years ago. It clamped to my sliding table and used a threaded rod to move a stop. The thread on the rod had a pitch of 16, so two rotations of the rod moved the stop a fairly accurate 1/8”. I used a rip blade to get a flat bottom on the cuts.

My Old Box Joint Jig

After assembly, I did the final sanding, to flush the joints and to prepare for finishing. I covered the base with paper since it was already finished, and then applied several coats of polyurethane to the sides.

After Gluing Sides Together

This is the final result.

Final Result
Top View
Close-up of Kumiko
Extreme Close-up

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