Introduction: Kumiko Jigs - Japanese Woodworking
Kumiko is a traditional Japanese woodworking technique made of wooden strips to form various designs and patterns. There are no nails or metal fasteners of any kind. There is glue used occasionally but the majority of the pieces are friction fit into each other using various angles and grooves. This instructable will cover how to make the jigs needs needed to cut angles for kumiko pieces.
Now, let's get right into it!
Tools that I used:
Sawstop table saw - https://amzn.to/2ILhw5L
Jointer - https://amzn.to/2ILhw5L
Chisels - https://amzn.to/2yWx7Qc
Japanese handsaw - https://amzn.to/2Ne5jtm
Drill & driver set - https://amzn.to/2H0qTlG
Spring clamps - https://amzn.to/2Kp2FU8
CA (super) glue - https://amzn.to/2NgcnpG
Digital angel gauge - https://amzn.to/2NgXRht
The jigs are best made with a hardwood. I used maple for the body of the jig and cherry for the stop blocks. Most hardwoods (like oak, ash, hickory, etc.) should work just fine.
Brass threaded inserts - https://amzn.to/2MECrtq
Brass thumb screws - https://amzn.to/2z6tlDY
Insert installation kit - https://amzn.to/2yZRMCM
Step 1: Mill and Square Lumber
This step is not applicable if you're using pre-milled and square lumber.
It is very important to have square material when making a project and even more so when you make jigs for a project. The jigs are the template so take your time to make these accurate.
In this tutorial I'm making three jigs, each at different angles. I mill enough lumber to make the three jigs out of the same piece of wood. Each jig ends up being 9" long so I mill a piece of maple that is 27" long.
I start with rough-sawn maple so I use my jointer to flatten and square two perpendicular faces. Now that there's flat reference surfaces, I can flatten the other two faces using my planer and table saw. When at the table saw, I also rip my material to the final 2 1/2" desired width.
Step 2: Cut the Groove
With square stock, we can now move on to cutting the groove. Here I made a mistake and made my grooves too deep. I made them at 1/2" deep but 1/4" is far more comfortable to work with when using the jigs.
There are many ways to cut this groove and I chose to use the table saw. With the blade height set to the desired groove depth (1/4") and the table saw fence set to 7/8", we can start cutting the groove. Here is where having the three jigs come from the same piece wood comes in handy. You only need to cut one groove.
You register the wood on the fence and make your first pass. Then flip the wood around to register the opposite face along the fence with the cut you previously made facing the table. Take a second pass over the blade then adjust your fence to make more cuts and remove the material between the initial cuts.
*Note: the bottom of your groove may not be smooth. To prevent this from happening, you can use a flat grind blade or a dado stack. If you don't have either of these, like myself, you'll need to sand the bottom of the groove to flatten it. The best way I found to do this is to wrap sandpaper around a wooden block that fits snuggly within the groove. Take your time and go slow to not mess up the walls or flatness of the groove.
Step 3: Cut the Angles
A digital angle gauge comes in handy here. It's very important to cut these angle as accurately as possible. I made my jigs at 45, 67.5, and 22.5 degrees. This angle gauge has a magnetic base. With that base on the table saw table, zero out the measurement. Then move the gauge to blade, make sure it's not resting on the teeth, and tint the blade to the desired angle.
With the blade angle set to 67.5 degrees, I'm actually cutting a 22.5 degree angle because we set zero on the table. The same setting is used to cut both of these angles. Cut one end of your work piece using a miter gauge or crosscut sled. Then cut the other end with the piece standing upright and along the fence. This can be tricky so be careful and do it at your own risk. I made a jig that straddles my fence for these types of cuts. I can clamp my work piece to this jig and cut it safely. It's important to make sure your work piece is square to the table. With the two ends cut to their respective angles, you can now set your blade back to 90 degrees and cut the jigs to length (9").
Step 4: Brass Inserts
These inserts are added so we can add an adjustable stop block to these jigs to make accurate and repeatable cuts. Drill the appropriate holes for your inserts. For the inserts linked in the intro, the drill bit size is 25/64". I added three inserts into each jig.
There is a tool linked in the intro that helps install the inserts after the holes are drilled. Here is a tip for installing the inserts without purchasing the installation tool.
Take one of your thumbscrews that fits the the treaded inserts and file the head into a hexagon. This doesn't have to be perfect. Just close enough that it can fit snuggly within a socket head. Now thread that screw into the insert and use a socket head in your drill the thread the threaded insert into the previously drilled hole in the jigs. Make sure the threaded insert is in deep enough and doesn't extend into the groove. Then simply unscrew your hex head screw and use it to install the rest of the inserts.
*Note - Brass is a very soft metal so be sure to drill the inserts straight into the holes to reduce the risk of stripping them.
Step 5: Stop Block
The stop block is part of the jig that will allow you to easily make repeatable and accurate kumiko pieces. Each stop block is made up of four pieces. Cut strips to size on the table saw and then cut one of those strips down into small blocks. Now glue two blocks between two of the longer strips, one on each end, creating a rectangular frame. I used CA glue for this because is dries quickly.
After the glue dries, trim the ends to make them flat and square.
Step 6: Adjustments
At this point I realized I made my grooves too deep (1/2") and trimmed down to height of the stop block.
Make sure the stop block fits within the groove and slides smoothly. Make any adjustments as needed.
The thumbscrews should fit within the channel of the stop block nicely and screw into the threaded inserts. If the flange on the screw isn't large enough to hold onto the stop block securely, you can add a washer under the screw to increase its surface area.
These thumbscrews are great and allow quick and tool-less adjustments. The downside is they only hold as tightly as you can screw them in by hand. To remedy this, I made my stop block long enough to be used with two screws at a time.
Step 7: Make Some Kumiko!
Congratulations!! You now have kumiko jigs! There are many patterns to explore but I recommend starting with the asa-no-ha pattern. It's the most common and the three angles discussed above are the ones needed to make it. Kumiko strips are commonly dimensioned at 1/8" x 1/2" and basswood is a great and inexpensive wood to learn with. Other soft woods like pine and douglas fir are great too but I find the best results come with using basswood. Feel free to ask questions down in the comments and I'd love to see photos of the one make!
You can watch the video here on how I built these jigs.
You can also find me on Youtube
Instagram to see what I'm currently working on
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