Introduction: DIY: Milling Kumiko Strips With Power Tools
One of the most frequent questions I get asked about kumiko is how I make the strips that make up the patterns. I think people see it as a ton of tedious work, so I wanted to share my process.
I make my strips using common power tools: a jointer, a planer, and a table saw. This is just one of the methods to make kumiko, but I find it efficient, consistent, and not too tedious.
3/4 or 4/4-thick basswood stock
Step 1: Selecting Lumber
Selecting lumber carefully is a critical step to getting consistent Kumiko strips. I make Kumiko mainly from basswood I get them from my local lumber supplier, only using other hardwood for accents. I use basswood because it's soft without being brittle like pine, it's cheap, and relatively plentiful.
I’ll start with 3/4 or 4/4 boards — anything thicker than that is just a waste of wood because I'm going to plane it down to a 1/2" final thickness.
When I am at my hardwood supplier, I'm looking for basswood that has straight grain, not too much color variation, and no twist. Any tension in the board to start will be there after milling too, so I just try to find something straight to start with. I can deal with bow, since I'll usually buy 9' lengths and cut them to 36" sections before I start milling.
Step 2: Jointing the Stock
The first real step is to get one edge (long, thin side) and one face (long, wide side) completely flat and square to one another, and I do this at the jointer. Starting with the face, I'll make passes over the jointer — careful to keep my hands away from the cutter-head — until the board is making complete contact with the cutter throughout the entire pass. Then I'll move on to the edge.
To joint the edge, I place the face against the jointer's fence to get a perfect 90° angle. I'll repeat the process of jointing the face, but this time for the edge.
Side note: I start with the face because it's so much easier to reference a wide face on the fence to get a perfect 90° angle, than to reference a thin edge against the fence.
The table saw method I use counts on consistent pieces right off the saw, so it’s critical to start with square and flat stock. I’ll spend a little extra time at the jointer to get a good result and set myself up for success.
Step 3: Planing the Lumber
After I have all of my stock jointed on one edge and a face, I’ll head over to the planer to flatten the opposite face. I’m lucky to have access to this 20 inch helical head planer, which saves me a lot of time. But you should be able to do this no problem with a lunchbox planer.
With the jointed face against the table, I’ll plane the boards until I get to around a half inch thickness. Thickness should be determined by your project, but 12 millimeters or a 1/2" is pretty standard for most smaller projects.
Step 4: Cutting the Cross-Laps
Now that I have a half-inch thick board, I start cutting the cross-laps. They’re the joinery that makes Kumiko possible, since they can take the pressure of the infill pieces pushing against them.
For square and diamond patterns, cross-laps are cut halfway up the thickness of the piece so two pieces can slot together. For hexagonal patterns it’s different, but that’s a tutorial for the future. So blade height is pretty important here. We don’t want the blade too low that the pieces won’t sit flush to each other, but also don’t want it too high that there’s a large air gap between the joints. So I will set the blade to be about half the thickness of the piece, but then raise it a little more. It’s better to err on the side of having the blade slightly too high.
Now I use the grooves in the base and a hardwood key to register the cross-laps. This will act kind of like a box joint jig. After the first cut, each of the next cuts will be registered in that key to ensure a consistent frame size.
Step 5: Ripping Thin Kumiko Strips
Once all of my cross-laps are cut, I set up for the strips. I move the fence to the blade and set the width using a story stick. Since I cut these cross-laps with my table saw blade, I need my story stick to match that thickness precisely (a hair too thick is even better to get a tight fit).
This story stick has been sized perfectly for the thickness of the kerf of this blade, so I don't need to measure it every time. I lock down the fence when there is no more gap between the story stick and the tooth of the blade, and now I’m ready to make my cuts. I'll run the Kumiko stock through the saw, ripping a strip from between the saw blade and the fence.
Now, you can totally cut Kumiko strips on the table saw in other ways, like with a thin-rip jig. If that works for you, use it. It doesn’t work for me, so I use this method.
There are five ways I keep myself safe in this operation:
- I set the blade height properly, to about one-half tooth above the workpiece.
- I use a push-stick, and not one of those long-necked ones. I use a block which provides both downward and forward pressure all the way through the cut. And yes, the push block is getting cut by the blade. I go through a lot of push-sticks. But that’s exactly what they’re for. I replace the push-stick when there’s very little area on the heel for pushing the piece through.
- I put pressure on the workpiece toward the fence, but only behind the blade.
- I always have my eyes on the workpiece at all times.
- If there’s some sort of issue with alignment of the workpiece, I just let the saw eat it. It’s just wood, and I can always rejoint it.
One final note is on the saw I’m using: Yes, I use a professional Sawstop cabinet saw most of the time. But I’ve also used a jobsite saw to do the same task. It’s just that the cast iron top and the fence of the Sawstop produces much squarer, more consistent results, so I will use this tool when I can.