Making Kumiko Thinner

I was recently working on a couple of projects where I wanted to use extra thin kumiko strips.  My goal was to make strips around 2mm thick.  I started the process using the method I described in the previous blog post, but when I started hand planing the strips I soon realized that the strips were now so thin and flexible that they were being pulled up into the blade even after I had reached the set thickness.  The issue got me thinking more about using a hikouki kanna and a different method of holding the strips that keeps them in tension rather than pushing them against a stop.  By holding them in tension you can avoid the issue of thin strips buckling and flexing which can happen when using an end stop.

A simple method of holding the strips in tension is to use sharp pins, inserted into the end of the planing beam, that dig into the kumiko and hold it in place.  Kumiko strips are placed over the pins and tapped down with a hammer. Its incredibly important to make sure the pins are short enough that they don’t get swiped by the plane when thicknessing.

For my stop I used nails that have been tapped into a removable piece of wood, then clipped nice and short.  A bit of trial and error with this method led me to file the pins to sharp points and slightly angle them away from the direction I was planing.  Angling the pins helps the kumiko to stay locked onto the pins and held down to the planing beam as the kumiko strips are put in tension while planing; in this way they act more like hooks.

 

I started using the pin stop along with my usual smoothing plane with a couple strips of wood (about 2 mm thick) double-stick taped to the sole.  The pin stop eliminated any buckling and flexing, but I was still having problems with the strips ending up thinner than I wanted.  I think the problem is that with really thin kumiko, even though the material is held in tension, there is still enough flexibility that once the blade engages it has a tendency to pull the strip up into the blade when cutting.

This is where the hikouki kanna comes in.  This plane has a build in spring-loaded bar that pushed the kumiko down onto the planing beam, effectively eliminating the above problem.  I had never used one of these planes before, but I took a gamble that it might solve my problem, and I set about making one.  It happened to be the first dai (wood body of the Japanese plane) that I’ve ever cut… I had a few mistakes, but in the end had a usable plane.

Here is the result, a hikouki kanna complete with a spring-loaded pressure bar and removable side tracks.

 

Here are the removable side tracks.  These extend beyond the surface of the plane sole by a bit over 2mm, but can be made to accommodate any kumiko thickness.

 

 

Here you can see how much the pressure bar extends beyond the surface of the sole of the plane.

 

And when it’s depressed….

 

 

And turns out it works!  And it works pretty well.  I was able to plane my kumiko strips down to just over 2mm with a very consistent thickness.  The pressure bar seemed to serve it’s purpose and worked well to prevent the kumiko from pulling up into the blade.

 

I think I’ll use this setup, the pin stop and hikouki kanna, for most of my kumiko work from now on.  It’s much more versatile, by not having to cut a groove in a planing beam for every different kumiko thickness.  Instead you just make different side tracks that attach to the plane, like these made for 1/8″ kumiko…

 

And the result and what all this was for…. a nice consistent stack of strips.

 

All for some goma gara pattern coasters made as a thank you for some generous folks I met on a recent trip to Japan.

 

And also for some new experiments…..

 

Thanks for visiting