Japanese Handplanes: The Kiwaganna Skewed Rabbet Plane

I made myself a snowball
As perfect as could be.
I thought I’d keep it as a pet
And let it sleep with me.
I made it some pajamas
And a pillow for its head.
Then last night it ran away,
But first it wet the bed.

Shel Silverstein

In this article your humble servant will introduce a Japanese plane called the Kiwaganna, meaning “skewed rabbet plane.”

This is an important handplane in common use in Japan, although not well known in the West. But there are enough people who own this tool and who struggle mightily to master it, that an explanation of some of the solutions your humble servant has learned over the years from senior Japanese craftsmen, and acquired during many decades of brutal study at the University of Stoopid, School of Hard Knocks (Lower Outhouse Campus), may prove useful.

What is the Kiwaganna Handplane?

The Japanese Kiwaganna is written 際鉋 in Chinese characters, and pronounced kee/wha/gah/nah. “Kiwa” means “edge” or “verge,” and “ganna” means handplane.

While the design of the Japanese version is unique, as far as your humble servant is aware, many other versions exists around the globe. This plane can handle a number of tasks, but it specializes in planing a straight-sided groove or rabbet right up to an edge or line with a clean 90˚ inside corner. A common application is planing the tongue around the perimeter of a board to make the bottom of a drawer, or a panel in frame and panel construction.

The skewed blade found in the kiwaganna is also not unique to Japan, but the Japanese version has some advantages, including simplicity, rigidity, and reduced weight.

In general, a skewed blade in a rabbet plane provides two benefits. The first is that the reaction forces pushing back on the blade include a vector that tends to push the plane towards the line, edge, inside corner or verge being planed to, making the plane more stable in the cut, an important factor where precision is necessary.

The second and most important benefit of the skewed blade is the smoother cut and reduced tearout it makes possible, especially important when planing cross-grain.

The other benefit the skewed blade provides in the case of the Japanese kiwaganna is the point of the skewed blade penetrating the body of the plane and ending flush with the side of the body, making possible a zero-clearance cut to a line without the extra weight and cost of complicated mechanisms and reinforcing plates. It’s a deceptively simple but clever design.

Craftsmen who use kiwaganna typically own a two-piece set comprised of a right-hand and left-hand version to deal with tight access and changing grain direction. But the right-hand version is the most popular by far.

This plane is of course used by joiners, cabinetmakers, sashimonoshi and furniture makers, but you would be surprised at how popular it is with carpenters and timber framers for cleaning the 90˚ inside corners of joints such as tenons.

Points to Keep In Mind

While a simple tool, the kiwaganna often proves frustrating to first-timers. Indeed, your humble servant struggled with kiwaganna for far too long before he figured them out. To avoid similar damage to brain and ego, Beloved Customers that wish to become proficient in using this elegant tool will find it useful to understand the following nine points.

1. First, a brief inspection of the body and the cuts made to receive the blade will show that kiwaganna dai (body) are more fragile than that of regular hiraganna planes, so when adjusting the blade, please use a wooden, plastic or rawhide mallet, not a steel hammer.

2. When removing the blade, strike the dai at the same angle as the blade is inlet into the dai to reduce unnecessary stresses. This means you will hit the top corner of the dai on the side opposite where the blade’s point exits. Clip off and round over this corner of the dai with a knife or chisel to prevent your mallet from chipping the dai. Striking the opposite corner can have bad results.

3. The right and left side edges of the blade must fit the retention grooves tightly where they exit the top surface of the dai. If the fit is too loose, the blade will be difficult to keep in alignment, but if the fit is too tight the blade may crack the dai during seasonal shrinkage. Older dai are usually safe, but a plane shipped from a wet Tokyo summer to a hellishly dry Arizona may experience problems. This article provides more details about fitting the body to the blade.

When shaving the grooves, work very slowly and carefully. Color the blade’s side edges with pencil lead or marking pen ink. Insert it into the grooves and note the high colored areas. Shave these down just a tiny tiny bit with a very sharp chisel, then insert the blade and check. Repeat as necessary. Don’t create a big gap between the walls of the groove and the sides of the blade (versus face and underside of the blade which must be tightly pinched in the grooves), just make sure the blade is not wedged tightly between the grooves.


4. Sharpen and polish the blade and uragane (chipbreaker) well and make sure they fit each other tightly without a gap near the cutting edge. The skewed nature of the blade and chipbreaker make this difficult to judge, so exercise caution. In many cases, the plane will work just fine, and maybe even better, without its uragane. The uragane has a bevel ground into its pointy corner. Make sure this is not touching the dai when inserted properly. Keep in mind that you will need to periodically grind this bevel down after sharpening the blade every few times or it will touch the dai creating a restriction where shavings will become jammed. When you sharpen the blade, you will also need to resharpen the uragane too to ensure they match each other tightly. Not every time, but once in a while. A lot of people fail to maintain the uragane and then wonder why they stop working.

5. Check that the “ear” of the blade (corner at the cutting edge opposite the pointy corner) is ground back enough so it is not inside the groove, because if it is, shavings will become jammed.

6. Contact between the back of the blade and the block should not be too high-pressure, otherwise the area on the sole behind the mouth may be pushed out making the plane misbehave, a common problem with this plane. You want even pressure to ensure the blade is stable, but remember that it is the grooves pinching the blade that keeps it in place, not pressure on its back.

7. With the blade fitted to the grooves and most of the pressure relieved from its back, insert the blade. Check that it projects evenly from the mouth its full width. This is very important. If it projects further on one side than the other, resharpen/reshape the cutting edge so it projects perfectly uniformly. This uneven projection is almost always the result of inattentive sharpening. Besides projecting uniformly from the mouth (when the sole is at the mouth is perfectly flat), the point of the blade must penetrate the dai (body) and be flush with the outside surface of the sidewall. Failure to get these two subtle details right is the most common cause of failure to perform in the Kiwaganna plane.


8. The mouth opening, in other words the gap between the blade and the sole of the dai where it exits the dai, must be narrow, and even in width, but not closed or skewed, otherwise shavings will jamb in the mouth, another common problem with kiwaganna. If the mouth is not even, use an adjustable steel protractor to match the angle of the blade measured from the side of the dai where the point of the blade exits. Remove the blade and mark the mouth with a sharp marking knife so the mouth is exactly the same angle as the blade. When doing this layout, be extremely careful to make the mouth opening of uniform width to match the cutting edge, but keep the mouth as narrow as possible. Use a sharp chisel to cut to this line making the mouth perfectly uniform. Insert a thin knife blade or sharpened utility knife blade) into the mouth to shave and clean it after chiseling.


9. There is nothing wrong with leaving the sole perfectly flat instead of having hollowed-out areas typically added to standard hiraganna planes. Just make sure it is truly perfectly flat. I have no problem with using sandpaper on float glass to true the sole of a kiwaganna, but a card scraper is a better tool for the job.

Juggling Blades

Although we addressed them above, let’s review the two critical factors you must juggle to keep a kiwaganna working well. I’m repeating these points not because I doubt Beloved Customer’s intelligence, but only because repetition improves understanding.

First, maintain the angle of the blade’s skew so that it projects a uniform distance from the mouth (with the mouth/sole flat and true). To do this you must pay more attention when sharpening the blade than is normally necessary. If you get this wrong, nothing will go right.

Second, as mentioned above, to cut into the corner of the rabbet cleanly, the point of the sharpened blade must penetrate the sidewall of the dai and be perfectly flush with the sidewall but without projecting out past the sidewall when the blade is projecting the right amount from the mouth and uniformly across its width. If the skew of the blade is wrong, or the dai is warped or worn, this point will end up being either recessed inside the sidewall or projecting outside it. It needs to be flush with the sidewall. If it is not, you may need to either shave material from the side of the plane (not recommended) or grind down the side edge of the blade near the point, a drastic measure. This is seldom necessary, and when it is, the reason is almost always a badly warped dai.

As you can see, this is a juggling act, but so long as you focus on these two points, and maintain the proper skew angle, all the blades will remain spinning in the air grinning from ear to ear.

YMHOS

If you have questions or would like to learn more about our tools, please click the “Pricelist” link here or at the top of the page and use the “Contact Us” form located immediately below.

Please share your insights and comments with everyone in the form located further below labeled “Leave a Reply.” We aren’t evil Google, fascist facebook, thuggish Twitter and so won’t sell, share, or profitably “misplace” your information. If I lie may my kiwaganna planes all warp to resemble mushy bananas.

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