Ha-ganna (葉鉋)

The Kanna

These planes are highly specialised, and used only in kumiko-zaiku. They have no other use, and having one alone is of very little value. Without these planes, the very minute and highly elaborate patterns would be extremely difficult and far too time-consuming, and therefore cost-prohibitive.

Ha-ganna

They were developed many years ago by the Japanese Tategu Craft Association to speed up the process of cutting the small pieces for the various kumiko patterns.

There are four planes in this group and they are designed to cut at 60°, 45°, 30°, and 15°.

These photos show the 45° plane. I use this to cut the pieces for the square asa-no-ha, and a couple of other lesser known patterns.
The second and third photos show the blade in detail. This is obviously the critical part of the plane. For this plane, the blade is bent at about 90° give or take quite a few degrees, but this angle isn't particularly important.

45° Ha-ganna 45° Ha-ganna45° Ha-ganna

These planes were made for me based on an order, and when I received them, the angles they cut were nowhere near their proper cutting angles. It's up to the user to tune the planes so their cutting angles are correct.

So instead of the angle at which the blade is bent, the critical parts of the blade are those parts I've marked with the read and blue arrows. By pure trial and error, each side of the blade has to be sharpened so they both cut at (in this case) exactly 45° each. If too much is taken off at the vertex (red arrow) the cutting angle is too low, and if too much goes at the edges (blue arrows) it's too high.

Once one side has been done, the other side has to be sharpened. And because the blade is hand-forged and hand-bent, the sides are not exactly equal in width, so this can't be used as a gauge. Trial and error for each side, all the while making sure that the sharpened edges join cleanly and exactly at the vertex. Consequently, even if one side cuts at exactly the correct angle, if more has to be taken off the other side in the process, the correct side will have to be sharpened again so that the edges meet at the proper spot. If absolute care isn't taken with this subsequent sharpening, the angle can be thrown out again, and it's back to the start again for both sides.

Use

How are they used? For the landscape I made in this example, I used the asa-no-ha and the kawari-yae-zakura. For the asa-no-ha, I use the 30° and 60° planes.

I cut six kumiko together (this is a comfortable number to work with), and butt the ends up against the end stop on my jig (These photos were taken a few years ago, and I now use a different jig — I no longer have an end stop, and butt the ends up against the side of the
kanna; methods and jigs change with experience).

Ha-ganna cutting
The ends have already been cut to a 60° point so I set the 60° plane against the end of the jig. The fence on the plane has been set so that it cuts the kumiko at exactly the correct length.

Ha-ganna cuttingHa-ganna cuttingHa-ganna cutting
One easy swipe across, and the plane has cut a 60° "V" trench across the kumiko. The bottom of the "V" is just below halfway through the kumiko thickness. I then flip the kumiko over and cut the other side, thereby cutting through the kumiko.

I then repeat this process with the 30° plane…

Ha-ganna cuttingHa-ganna cutting
then back to the 60° plane, and so on. Provided the planes are properly tuned and the fences are properly set, what I end up with are identical pieces with one end 60° and the other end 120°.

And this is how the
asa-no-ha pieces are fit together.

Ha-ganna cutting
Here are some more photos showing the cutting process with my current jig. I'm cutting Huon pine to give me end points at 90°. Exactly the same process as I described above, but this time with the 45°
ha-ganna.

Ha-ganna cutting 02 Ha-ganna cutting 02 Ha-ganna cutting 02 Ha-ganna cutting 02 Ha-ganna cutting 02 Ha-ganna cutting 02


These planes were not cheap, but they're worth every yen I paid for them. All the patterns I've described in the kumiko pattern section can be made without these planes. All that's required are accurate jigs and a sharp plane. They are essential, though, to make the very small angled pieces that are only a couple of mm long.

Ha-ganna pieces Ha-ganna pieces
They also speed the process up tremendously. It's estimated that these planes can deliver a ten-fold increase in speed over the former method of using jigs. My competition lamp had over 7,000 pieces, and HANABI landscape over 10,000, but I've seen work in Japan that consists of over 120,000 individual pieces. Purely on time alone, work on this scale wouldn't be possible without these planes.


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