Kumiko Table Saw sled – Making Shojis part 2

 

I left off the last post on making shoji screens at the point where I had just milled a fresh stack of kumiko.

 

After milling all the vertical and horizontal strips to 1/4″ wide by 1/2″ deep it was time to cut the half-lap joints.  Since I had 8 screens to make I decided to set up a table saw sled to cut the half-lap joints instead of cutting everything by hand like I usually do.  The sled is basically no different than a standard table saw sled.  It’s setup with a pair of runners that sit in each miter slot, and the fence is accurately aligned to cut exactly at 90 degrees.

Below you can see the sled as I had it set up to cut the kumiko tenons and half-lap joints.  The process here is very similar to how a table saw sled can be used to cut box joints with a registration key.  The difference with cutting joints in kumiko is that the spacing between cuts is much farther apart.  Below you can see the key as well as a couple of slots that are used to hold the key for different spacings.  The Blocks that are screwed down to the jig are really unnecessary, but I thought that I could used them to hold the kumiko tight to the fence.  I ended up removing them eventually and just used my hands to carefully hold all the kumiko securely in place, but an alternative would be to use some type of feather board setup.

One very important note is that the saw blade/dado stack needs to be sized so that the finished cut will be the right size to fit a strip of kumiko.  If you are limited by the size of the blade/dado stack then the only other option is to size your kumiko to the size cut that the blade makes.  In this case I ran a few test cuts before milling my kumiko and I ended up sizing them slightly thicker than the resulting cut made by my 1/4″ dado setup.  Having the kumiko extra thick then allowed me to take a few final plane shavings after cutting all the joints, until the half-laps came together with a nice friction fit.

 

Here is the setup for the first cuts which will make the tenons on the end of the kumiko.  The piece of ply, marked 1 and 2, has a groove cut in it on the underside that registers on the key from the previous photo.  The stop is set so that I can slide a stack of kumiko up against it to cut short tenons at a length of 1/4″.

 

For the tenons the depth of cut is 1/8″, so after cutting one side the whole stack is flipped to cut the opposite side, forming a 1/4 x 1/4 tenon.  Here is a bad close up showing the result after the first cut.

I repeated this process to also cut the tenons on the other end of all the kumiko strips.

Once the tenons were cut I could then remove the stop block and reference the shoulder of the tenon against the key for the first half-lap joint.  I also had to raise the blade to make a 1/4″ deep cut (half the thickness of the kumiko).

 

After sliding the stack against the key I could make the first cut.

 

And here is the result.  A nice clean half-lap joint in each piece of kumiko.

 

The next step requires a bit more explanation.  For these screens there are 13 vertical kumiko and the spacing between each vertical is only about 2 inches.  So in the horizontals that I’m cutting now, that makes 13 notches spaced 2″ apart.  Instead of cutting all those notches along one side of the horizontals, they alternate from front to back.  So after completing the previous cut at 2″ from the tenon shoulders, I now need to flip the stack and make the next cut at 4″ from the tenon shoulders.  Does that make sense?  I hope so, and if not hopefully the pictures will help clarify things.   In order to make the cut at 4″ I needed to move the key to a new location, seen below.

 

With the key now set at 4″ from the blade, I could do as I did before and set the stack of kumiko against the stop and make the next cut.  Here is the result.

 

The rest of the process is pretty straight forward.  From here on out I could leave the key in it’s location at 4″ from the blade and continue cutting the remainder of the half-lap joints.  For each new cut I simply slid the whole stack until the previous cut registered on the key, and then carefully cross cut the next set of joints.  The process was repeated all the way down the stack and on both sides of the stack.

 

Here is how the horizontals looked after cutting all the half-lap joints.

 

Now on to the the vertical kumiko!

 

Here are the tenons completed in the same way as I did for the horizontal kumiko.

 

For the half-lap joints I used the same process as above, but for the verticals all the joints get cut on one side so there is no alternating back and forth, which simplifies things.  The spacing between each joint was also much greater at around 8″.

 

 

And here are the screens after assembly of the kumiko.  You can see a couple of the screens have the border frame attached (aka tsukeko), and I’ll cover more on that in a following post.

 

I had fun stacking theses grids and playing with the light….. ideas for a future sculpture perhaps…..

If you look closely you can see the alternating vertical kumiko.  A benefit to alternating like this, especially when the spacing is fairly tight as it is here, is that it helps keep the grid flat.  If all your joints are on one side, and if they happen to be on the tight side then it’s very easy to have an assembled grid with a pronounced curve to it.

 

Well that’s all for now.  Hopefully this is a helpful post for those looking to use an alternative method for cutting joints in kumiko.  I still like to cut joints by hand, but if you have to make a lot of cuts a simple table saw sled can work really well and can really speed things up.  That being said, setup is really important, so take the time to do some test cuts and make sure you have your sled set up accurately.  Thanks for visiting.