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Ito-ura and problems

The blade ura is one area that highlights where there may be problems with either the sharpening technique, or the ura-dashi and ura-oshi technique. I cover this in some detail in the book, and I thought I would include this section from the book here, because the ura and trying to maintain it in its optimum shape certainly is one aspect that can cause a degree of frustration and exasperation.

This is directly from the book. It is, of course, not the book layout. The copyright marks on the images are purely for the internet. They are not in the book.

Shokunin in Japan are very particular about how the blade ura looks. It can be a source of pride, or it can cause shame and embarrassment. A properly shaped ura not only makes the blade and the kanna more efficient, but is also a testament to the shokunin’s skill and his respect for his tools. A badly shaped ura shows a lack of care that is more than likely to be carried through to the shokunins work.

In this section, I’ll describe in detail how to create and maintain an
ura you can be proud of, and how to avoid the bad habits that will prevent you from achieving this.

The type of
ura to aim at is an ito-ura.

01 P27

Ito is the Japanese word for thread, and in an ito-ura the uraba is as thin as a thread, or in reality about 1–2 mm. The hard steel and soft iron lamination structure of a kanna blade is different from that of a chisel, so they have different ura, as shown in Photograph 28. The chisel ura is broader, and is known as beta-ura. A reasonable beta-ura is normal on a chisel, but not on a kanna blade. This is the type of ura you should avoid.

02 P28

There are a number of faults that can create a badly formed
ura, but the advantage is that they all affect the ura in a different way so if you are having difficulties in obtaining or keeping a good ito-ura, the ura itself will tell you where the problem is.

The main faults are: a failure to tap out adequately, and closely linked to this, honing the back too much, especially on the coarser grits; an uneven distribution of strikes when tapping out; honing along a single line; honing at an angle not perpendicular to the stone; and, perhaps the most common, allowing the blade
atama to sag while honing.

Failure to tap out adequately
This can be a common problem when tapping out from the uragire condition, but it can also occur if you don't properly tap out a new blade that has a slight elevation at a point along the cutting edge. This aspect was covered in the Adjusting a new plane section beginning on Page 25.

The following diagram shows what happens when the tapping out is inadequate. This can often be caused by a degree of tentativeness when tapping out, especially in the early stages. Although not as bad a problem as not tapping out at all (see Page 39), over time the problem will continue to worsen.

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The way to solve this is very simple indeed. If, after tapping out, you hone the ura on the coarse stone and the scratch patterns reach both sides of the blade but the uraba has not widened sufficiently or not at all, STOP. Don't try to force out the uraba on the stone.

If you continue honing until a reasonable
uraba appears, you will hone too much, and while you may end up with a thin uraba, the ashi on both sides will be too thick. Once this happens you are virtually stuck with fat ashi for the rest of the life of the blade.

This is also the case if you don't tap out adequately on a new blade. If you’ve tapped out adequately but hone too much on the coarser stone, you will end up with a

Tapping out must be a careful and deliberate procedure, but that does not mean you should be tentative. Tap, check, tap, check, and continue until a sufficient bulge appears, regardless of how long it takes.

Uneven tap distribution
In this case, tapping has been concentrated too much in one area so the bulge in the urasuki isn’t uniform. The following diagrams show what happens when the tapping is not even.

(1) Tapping too much or too strongly in the center and not enough on the sides: This can be a tendency in the early stages, where the center seems the safest.

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(2) Tapping too much or too strongly to one side: This quite often happens if the uragire is more to one side, and you fail to account for it .

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If you find that your uraba is beginning to look like this as you hone, in either of these cases, simply stop and tap out some more in those areas that are too shallow. An uraba that’s too wide can be fixed after a few sharpening sessions, but once one or both ashi become overly wide, that’s the way they’ll remain.

Honing along a single line
If you hone the ura along a single line on the sharpening stones you will create a ridge, which is another sign of poor technique. Therefore as you hone the blade along the stone, especially the coarser grit stones after tapping out, gradually move it backward and forward 10–20 mm to prevent the ridge from forming.

06 D44

Honing at an angle
When honing the ura, the blade should be perpendicular to the length of the stone. If the blade is at an angle you run the risk of an ura that looks like the following.

07 D45

Sagging atama while honing
This is perhaps the most commonly seen fault. Kanna blades are quite large and heavy, and there is a tendency to let the atama sag while honing the back, giving the ura somewhat of an hourglass shape. The following diagrams show this.

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09 D47

When honing the back, you should have a feeling that you’re lifting the
atama up slightly with your supporting hand as you apply pressure to the bevel with your other hand.

10 D48

You shouldn’t actually raise the
atama as this would give you an unwanted back-bevel, just feel as though you are. That way you are giving the blade proper and even support, and you’ll avoid the hourglass shape. Unfortunately, once you have the hourglass ura, you’re stuck with it until you’re able to sharpen past it, which could take several years.

I mention earlier in the book that a properly formed ura is not just a matter of aesthetics. There is a very sound reason for the ito-ura and avoiding ashi that are too wide. Hopefully the above can go some way to help you achieve that.

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