Daed Toolworks

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Kumiko – I just can’t quit you!

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Before I get back to the planes I’m trying to finish up, I want to go on to a bit more of the Ranma project I’ve been working on this week in between coats of french polish.  The traditional square network of kumiko in shoji are relatively straightforward, with lap joints at each intersection.  The triangular, or diamond pattern, however, is a fair bit tricker as each node of the lattice involves three members to join.  I don’t know of any written information in english on the techniques for this — though there are some sketches in Nakashima’s Soul of a Tree. I pestered a couple of expert shojimakers in the US while puzzling out the details, and I thought I’d put up a not-so-brief summary of the basic techniques and joinery.

I’m going to try to document this as well as I can without taking 2 hours of your time, but please be forewarned that it may be a bit confusing at first.  It may help to have a look at the final piece first, to get a sense of what we’re working toward.  Here is a roughly 24″ x 7″ section of diamond-pattern kumiko that I’ll be using in the final ranma:

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In order to make the ‘grid’ work, there are three different members of the lap joint that have to be employed – one for the horizontal pieces, one for the ‘left leaning’ pieces, and one for the ‘right leaning’ pieces.  Here are my test sample pieces:

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All of these joints are cut at 60-degree angles, and 2/3 of the depth of each piece is removed.  Exactly how to remove them for a good fit is the tricky part.  In order to make these cuts (I’m cutting at least 60 of each for this piece) I use a purpose-built small miter box with a kerf exactly sized to my dozuki.  I also use small guides clamped to the sawplate to precisely gauge depth of each cut.
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For the first piece, you cut a left 60-degree lap (all laps are 3mm in width to accomodate the 3mm kumiko) a full 2/3 of the depth of the kumiko. Then make a right 60-degree lap that exactly overlays the first, and to the same depth… gently remove the waste with your narrowest chisel. Here’s what that joint should end up looking like:
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The second joint, gets a left 60-deg lap, but to just 1/3 depth.  Then you flip the piece top-for-bottom and cut the same joint from the other side.  Again – these need to exactly overlap.  The dead center point of each joint will be the same.  Here is what it should look like at the end – notice that although you cut both laps in the same direction, the ‘flip’ means that they’re actually opposed in the final piece.

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The third cut is even more interesting.  Start as with the first, with a left 60-deg  lap to 2/3 depth.  Then make a right 60-degree lap, but this time go to only 1/3 depth.  When you remove the waste, you should have the following:
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Now, it’s time to gently fit these and see how accurate we’ve been. Start with joint 3 (the odd one) on the bottom, and insert the joint 2 gently in place as so:

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If things are fairly clean, you should be rewarded with the following:

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If so, you can feel pleased – things will almost certainly work out just dandy. Joint number 1 should fit ever so gently into that slot, and leave you with a perfect, or close enough, three-way lap joint.

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Now – if you got this far on your first try – start a blog.  You’re a woodworking hero.  Most of us need to make a few stabs at it before we get everything reasonably ‘right’ for this.  Don’t fret – it will all make sense after the first couple of attempts.  After that, you just cut row upon row of each type, at exact intervals (I’m using 2″ on center for each joint) and you should hopefully end up with something like the ‘sheet’ at the beginning of the entry.
A couple of things to note:  first – you can gang-cut the pieces, but you have to pay attention to the offset of each piece in the stack.  Once you’ve made a couple of successful test joints, you’ll undoubtedly have no problems figuring that out if you remember to compensate for it.

Second – these joints are really made to be assembled ONCE and once only.  Assembling them compresses the fibers at each joint, giving you a fairly nice fit, but they will never go together that cleanly again if you take them apart.  If you look at that final test joint photo, you can see what I mean.  That piece was put together and taken apart twice before this picture, and you can see on the left and right edges of the joint where the piece has been somewhat crushed, making it feel ‘not so fresh’.

OK – so that’s it for the basic diamond pattern.  The ‘infill’ patterns to make the hemp leaf (as no ha) design will have to wait a few days at least. The french polish on my planes is just about ready, which means I’;m going to be peining and making a lever cap in the next few days.


NOTE:
 I want to pause briefly here to let both of the readers of this blog know that no matter how poor the title of this entry was, you have no idea how much worse it almost was. Now normally I’m a lover of the finer things in wordplay as well as tools, but there are some times that even the most pathetic specimens of wordplay can worm their way into  even the most refined bloggibitionists’ prose. Especially in the title…

Let’s be honest, here — it just ain’t in a man’s nature to gracefully decline the savage temptation of titling a shoji blog entry “Lattice Begin” — to say nothing of its flashier, drunker sister “Lattice pray.” Sure it’s easy to toss “Kumiko Chameleon” onto the scrap heap of really really bad ideas – but who among us wouldn’t be drawn to the trailer trash siren song that is “Kumiko – you get there faster if you take it slow”?  (And to think – Mike Love was the SANE one).  Even strong men must at times swoon ‘neath such strains…

But fortunately, I didn’t foist any of those monstrous succubi onto you, gentle reader.  You may now breathe a sigh of relief.

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Comments

  1. Multiple readers, I think, but two commenters.

    This is impressive work, and the lattice is beautiful. The intricacy of Japanese joinery burns my noodle. Even when it's hidden, it elevates simple joinery to art.

    Reply

  2. Beautiful work. This is one of those few examples where I'm more impressed by the patience it took to achieve it than I am with the capabilities of the craftsman in producing it. It is not that I am not impressed with the craftsmanship. It is just, well, wow, man, all those cuts!

    As an aside, I am looking for a custom made plane lever cap and for the life of me, I can't find an email link to you.

    Peace,

    Mitchell

    Reply

  3. Thanks G-$ – I agree about japanese joinery; frequently I think it's over the top, but it certainly reflects a remarkable level of craftsmanship.

    Mitchell – Hmmm… I could have sworn I put an email link up here – I'll add it later tonight.

    It's [email protected]

    As to the patience vs craftsmanship issue, I agree in large measure. But then I also tend to think that patience is one of the greatest components in most craftsmanship – or at least in developing mastery in any particular area

    Also – while there are an enormous number of cuts in this, bear in mind that most of them are 'jigged', and I'm generally ganging half a dozen or so kumiko together at a time. Once the setup is ready, I'd say it's a couple of hours at most to do all the joinery in this part.

    Reply

  6. Hi,
    I know it’s been a while since this was posted, but in the event that you still monitor comments, I wanted to thank you! I have looked all over for this information, and even now in 2023 it is like hens teeth. I was looking at a few hours trying different table saw set-ups (I had a basic idea of how to do the cuts) but you pointed out a couple of things I would have had to “trial and error” to get right. Beautiful work and I can’t thank you enough for sharing your knowledge.

    Reply

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