Japanese plane chip breaker cracked

[David Wong]

This is the second part in my series "What not to do when setting up a Japanese plane". In the previous installment, I showed the results of bad ura-dashi (tapping out) resulting in a badly cracked blade. Today, I am illustrating how I managed to crack the corners of the chip breaker.
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Excuse the poor photos, but you can see how the corners are cracked in a dog ear-ed manner.

https://lh3.googleusercontent.com/-WF-MLCTbCqM/U3_pyKi0RjI/AAAAAAAAAjo/wOOFzAjXOFA/w800-h600-no/DSC02014.jpg
​https://lh3.googleusercontent.com/-dQckXuhJhG4/U3_pw_29PDI/AAAAAAAAAjg/ZgT6nEFIO1Y/w800-h600-no/DSC02018.jpg

The damage occurred when I was fitting the chip breaker to the dai. The fit was tight, so I was using a combination of filing the mimi (ears) on the chip breaker, and filing the osae-bo (chip breaker pin). The main blade had very skinny lands on the back, so during the test fit, I must have had the corners of the chip breaker on the lands with the rest of the blade unsupported. This most likely resulted in the cracks. It took me several hours to grind and hone the chip breaker to correct the mistake. The chip breaker bevel is at 25° with an ~50° micro bevel. The chip breaker for this plane is does not have a maker's mark.

[David Weaver]

That's a bummer. Is this a plane with a signed dai?. Some of my unsigned dais have been short on room for the chipbreaker, which is strange. My signed dais haven't been so far, but I have one nimura dai that I haven't check yet. You may still have one of my other nimura dais (on one of the basic 70mm yamamoto planes).

[Mark Almeidus]

Sorry, i have a newbie question, but you said the chip breaker and the blade werent suported. Does that mean u dont use screws to tighten both of them? One of the planes i borrowed, the blade and the chip breaker were without screw, just sitting like that. So im using it without any screw. Does that make a diference?
U guys get realy deeply with this stuff, and the dedication and precision u are involved. Have to admire it :).

[David Wong]

Mark,

Traditional Japanese planes do not use screws to hold down the chip breaker to the blade. The blade, bevel side down, is held by slots cut into the side of the wood body. The blade itself is tapered in thickness, so that it wedges tightly in the slots. The chip breaker slides under a supporting rod, and is held in place by pressure between the support rod and the back of the blade. The "landings" I mentioned, are the raised flat areas on the back of the blade, which is slightly hollowed.

All this deserves a illustration, which I don't really have. You can look at this illustration I got from the Tsunesaburo website (http://www.tsune36.co.jp/top.shtml) to get an idea of the components of a Japanese plane. This shows a plane with the blade and chip breaker installed, cross sections of the wood body, and the back of the blade and chip breaker. Note both the blade and chip breaker have slightly hollowed backs, with only the area behind the cutting edge and the sides, being slightly raised and flat. The reason for the hollow is to make it easier for the back of the blades to be flattened. I am guessing that the corners of my chip breaker cracked because I had too much pressure on the chip breaker, and just the corners were touching the landings on the blade

Hope this helps answer your question.

http://www.tsune36.co.jp/images/zukai.jpg

[David Wong]

Is this a plane with a signed dai?

Both the dai and chip breaker are unsigned. I think the blade blacksmith is Fusaichi Yamaguchi, and the blade is named "white phoenix". I think this is probably a less expensive blade from Fusaichi Yamaguchi, based on the blade decoration, or lack of.

[Mark Almeidus]

Realy interesting concept, and a little bit complex.
Thanks for the info.