Specialist shoji/kumiko planes - ha-ganna

**Des.K.** · 6th January 2011, 08:47 PM

(1) Ha-ganna

It's been deathly quiet here in the Japanese hand tools section for the past month or so, so I thought I'd expand a bit on the hand planes I touched on slightly in the thread on cutting the three-way joint here.

These planes (ha-ganna 葉鉋) 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.

These planes were made for me based on an order I placed about 4 months before, 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.

As you can imagine, once the correct angles have been achieved, you protect those angles with your life

It took me about a week to get all four planes cutting at the correct angles. The 60° plane was especially difficult, because not only were the red and blue arrow angles critical, the actual sharpening angle also became very important.

In the second part after I've had dinner with my beautiful SWMBO, I'll show how these planes are used.

**Des.K.** · 6th January 2011, 10:24 PM

(2)

In the part above, I took the blade out of the 45° plane. In this part I'll show how they're used. I'm currently making up a landscape design, and for a part of this I use the asa-no-ha, and the kawari-yae-zakura, which is based in part on the asa-no-ha (the Patterns section on my website shows these different patterns in some detail). For the asa-no-ha, I use the 30° and 60° planes.

I tape six kumiko together (this is a comfortable number to work with), and butt the ends up against the end stop on my jig (photo 1). The side fence is due for replacement after I've finished this project.

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 (photo 2).

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 (photo 3).

I then flip the kumiko over and cut the other side, thereby cutting through the kumiko (photo 4). I then repeat this with the 30° plane (photo 5), 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° (photo 6).

The last photo shows how the asa-no-ha pieces are fit together.

These planes were not cheap, but they're worth every yen I paid for them. All the patterns I've described in my website 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. 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, but I've seen work in Japan that consists of over 80,000 individual pieces. Purely on time alone, work on this scale wouldn't be possible without these planes.

Hope this has been of some interest.

Des

**Sheets** · 7th January 2011, 12:59 AM

Hi Des,

Thanks for showing this. Though I've never made kumiko in any such complexity, I can imagine how difficult it can be to be consistently accurate. Its amazing what the tool makers can come up with, too.

At least having fiddled with the angles to get them right on, good Japanese steel will stay sharp for a long time and you won't have to fuss with them often. Or one would hope - you'll have to let us know how well they keep their edges with constant use.

Beautiful work as always.

Steve

**Des.K.** · 7th January 2011, 08:14 AM

Thanks Steve.

The blades hold their edge very well, but how the timber is cut is very important. With most of the Australian hardwoods I use, I cut the timber for normal kumiko (horizontal, vertical and diagonal kumiko) so the straight grain faces upwards (mitsuke), but for the small pattern pieces I have to cut it so the straight grain is on the sides (mikomi). This results in a nice clean "V" cut across. If not, the planed end of the kumiko piece becomes quite jagged (depending on the timber type), and it takes its toll on the blade edge. So most of my dimensional rough sawing and ripping revolves around the part of the board that presents a rift sawn grain pattern. There's a lot of fiddling around, and that's before I even get to the part of making the pieces.

Des

**tea lady** · 7th January 2011, 09:14 AM

Ear marked for reading later!

**NCArcher** · 7th January 2011, 10:21 AM

Thanks Des, fascinating as usual.

Congrats on the competition as well.

**Fuzzie** · 7th January 2011, 06:02 PM

I had the good luck to watch Des use these planes. I thought he was talking about a second mortgage when he mentioned their cost.

Watching him cut parts made me appreciate more than ever what sharp really means. To see the kumiko being cut, he made it look as simple as using one of those sliding paper sheet cutters.

"You still have much to learn Grasshopper." ...

**NeilS** · 9th January 2011, 03:36 PM

My mind boggles at the blacksmithing involved in constructing a blade like that. It would require a high level of skill and there would be very few that could do it. No wonder they are exy.

A bit like shoji making itself... which boggles my mind even more....

.

Thread: Specialist shoji/kumiko planes - ha-ganna

Thread Tools

Search Thread

Specialist shoji/kumiko planes - ha-ganna

Similar Threads

Shoji screens

Shoin shoji makeover

WIP - Shoji screens for bunkasai

Japanese hand plane (Hira ganna)

Shoji screens anybody?

Tags for this Thread

Posting Permissions