Sharpening japanese style

Sebastian Gonzalez
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Sharpening japanese style

Fri Nov 28, 2014 3:20 pm

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Last edited by Sebastian Gonzalez on Mon Apr 04, 2016 8:04 pm, edited 1 time in total.
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Chris Hall
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Re: Sharpening japanese style

Fri Nov 28, 2014 6:24 pm

Like what you're doing Sebastian - carry on!
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Dennis

Re: Sharpening japanese style

Fri Nov 28, 2014 7:46 pm

From someone that doesn't sharpen their own saws, all the encouragement in the world to you, Sebastian. It has become nearly an extinct trade in Japan now, with replaceable blade saws much having put the former standard ones out of use. Lots of nostalgia about saw sharpeners, hearing the tap tap tap as they set the teeth and removed warp as you walked by their shops, plus the atmosphere within where they worked. There used to be two brothers that I would go to on a quiet street, sitting side by side on an elevated platform, and one of the wives would bring you out a freshly made cup of tea while you sat on a stool and spoke with the guys about any aspect of saws. It was very sad when they had to close up. People have much forgotten the feel of a good saw over the lifelessness of the replaceable blade ones. Metate was one of those trades that someone could carry on well into their elderly years, as well.

You mention lighting, it pretty much used to be that Japanese liked to work sitting under a bare hanging light bulb. Sitting on the floor while working is an interesting topic. If your back can take it, there can be some advantages, as you say. Of course back in the ancient days when Japanese began those trades where they worked on the floor, they were much built lower to the ground themselves.
Sebastian Gonzalez
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Re: Sharpening japanese style

Fri Nov 28, 2014 9:39 pm

Thanks Chris, will do!

Dennis, what an amazing experience must that been. I found this picture from a photographer online and really love the atmosphere

http://timethemoment.files.wordpress.co ... ener1.jpg
And the tea, in general I make myself a cup before sharpening one saw. After each side one sip, helps to relax.

The sitting position, well, it's actually more comfortable for me that way. Standing I had to bend the neck too much to see the teeth, sitting everything is closer. You also need to be really stable, and standing that means that your whole body is very tense, while sitting is slightly more relaxed. Not that it gets easy, mind you, but it helps. (I add the ergonomic details because I found that to make the sharpening easier and faster you need to consider your whole body, it's not just your hands.)

I know it's sadly am almost forgotten craft in Japan... which is more reason to study it. Eventually I would like to make simulations of both, the saw and the wood, and study how the shape of the teeth affects the cut — I'm a physicist by formation, but my plan is to become a furniture maker in Chile next year when my contract in Austria finishes. It would be cool to have a smooth transition from one to the other.

Perhaps you know Nagakatsu, aka ChuMasaru? He's a metate in Kyoto and gives "lectures" on saw sharpening. He seems to be really pushing forward the "craft", he even visited europe twice, I think. I hope I can visit japan in a few years and learn from him first hand. I bet they will be surprised seeing a chilean sharpening saws.
De
Dennis

Re: Sharpening japanese style

Fri Nov 28, 2014 10:05 pm

Cool post, Sebastian.

Yes, Japanese are often keen on wanting to assist other races that are interested in the traditional trades. Japanese are a funny bunch, they often don't get to appreciate something until it is completely gone.

Unfortunately, I'm a long ways from Kyoto and haven't heard of Mr. Nagakatsu. Kyoto would be an interesting place to work, still a fair amount of tradition abounds. The last saw sharpener in my area was a guy that retired from a shop in a different location and had his work continuing in the entrance area of his house. Unfortunately, he passed away a number of years ago. One very nice thing about sharpeners, is that they could tune a saw to your liking, depending on what you wanted to use it for. The depth of skill that allowed such exactitude was quite profound.

What you mention about your body is a very interesting point. Physically orienting yourself to the tasks in such a way that brings the best performance is something that I heard talked about before in Japan One can get lazy about positioning. That was expressed to me when working on the floor over the bench. Everyone pretty much worked on the floor in that shop. Standing up, it seems to become a more unconscious thing, but working on the floor and smoothly centering over the task does require a dexterity of positioning that more requires a certain discipline, it seems.

Woodworking in Chile seems intriguing, good luck!
Matt J
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Re: Sharpening japanese style

Fri Nov 28, 2014 10:10 pm

Sebastian, this is great. I'm looking forward to reading more. Like the blog, too!
Sebastian Gonzalez
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Re: Sharpening japanese style

Fri Nov 28, 2014 10:23 pm

Dennis wrote: Standing up, it seems to become a more unconscious thing, but working on the floor and smoothly centering over the task does require a dexterity of positioning that more requires a certain discipline, it seems.
That's really interesting. I had this conversation with a friend of mine who is a Reichnean psychologist, in other words, a body language kind of guy. According to him the movement of the plane in japanese carpentry was a more inward movement, a movement that envelops the thing, whereas the western pushing movement is more given to a subject-object relation, a distancing from the thing. It kinda made sense to me but I'm too inexperienced in woodworking to actually see the difference in my own practice.

I do think that at the end those thing matters. We are bodies in a world and our life is what we do with those bodies, and how we do it...

Anyway,
Woodworking in Chile seems intriguing, good luck!
I guess it will be a lot of fun. I'm looking forward to have fewer resources and start making things instead of buying. That was one of the reasons I needed to learn to sharpen saws, otherwise I spend half my salary just shipping blades to Chile, or paying the ridiculous prices the one guy who sells asks for them.

I can see in a future learning that, sharpening saws for tasks. At the moment, I just have different saws with different geometries and each one likes one type of wood. I have a really aggressive rip ryoba that I guess is for pawlonia wood, I tried it with spruce and I broke a tooth. Other saw doesn't have problems cutting boxwood or rosewood. It's a really interesting world.
Sebastian Gonzalez
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Re: Sharpening japanese style

Sat Nov 29, 2014 8:17 am

Thanks Matt, glad you like the bog! and thanks everyone for the support.

Chapter 2: Some theory

First of all, let me introduce you to Nagakatsu-san. If not the best saw sharpener alive, at least is the one with the best PR. He's been in europe at least twice, gives lectures on saw sharpening in Kyoto, and has a website. Probably the only one with a website in japan: http://www.mitsurouwax.com/nagakatsu/

There is even an HD video of him: https://www.youtube.com/watch?v=4j5B6C0m15E

He also appears on a few blogs, like Douglas boatbuilder and in his saws Tanaka's videos. However, the turning point for me was a small diagram shown to me by Jason from mypeculiarnature.blogspot.com:

Image

The idea being that the best teeth geometry is not A but C, against what saw sharpening companies promote. Here you can read it all in japanese http://blog.goo.ne.jp/yui1415/e/b78d923 ... 9672741882 (would be great if someone can translate/summarise, I don't read any japanese, so everything is google translated.) The difference seems to be that a positive rake bites the wood while a negative rake slices it, producing a smoother surface. From the saws I have, I can say that it was a common practice to use a (slight) negative rake on the teeth.

That little diagram allowed me to put the problem in typical physicist terms. "How does the geometry of the teeth influence the cutting action, and how this depends on the wood to cut, ie, on the particular structure of the wood being cut?" From then for me it's easy because the problem is reduced, and you have a technical problem (how to actually file the teeth) and a research problem (relation between geometry and the cut). It's also nice because there is no proper research on the subject, I just found some papers on the angle of the teeth for circular saws. Anyway, enough geekness.

In the next chapter I will go into the details of the technical problem of filing metal in such a way to produce nicely shaped facets. If you divide to conquer, the problem is simply file the back facet, the front facet, and then the top eye (that's the order I use at least, seems to work best if you file the top eye at the end). Even more, if the teeth are good enough you only need to touch up the front and the top facet, as I've seen in some used saws.
Last edited by Sebastian Gonzalez on Sat Nov 29, 2014 8:06 pm, edited 1 time in total.
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Chris Hall
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Re: Sharpening japanese style

Sat Nov 29, 2014 10:02 am

Very interesting Sebastian.

I can help with the translation a bit. Here are the terms for the various parts of the tooth in a cross-cutting saw, or yokobiki (横引き):
18a69fced5151250a149df2ec554a888.jpg
18a69fced5151250a149df2ec554a888.jpg (38.18 KiB) Viewed 38328 times
The three parts are:

Shitaba (下刃): cutting edge

Uwame (上目): top facet/tip of the tooth. Another term for this part is 'katana no sentan' (刀の先端)

Se (): 'spine'
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Chris Hall
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Re: Sharpening japanese style

Sat Nov 29, 2014 10:05 am

This sketch was interesting, comparing a ripping tooth to a cross-cutting tooth:
05.jpg
05.jpg (82.72 KiB) Viewed 38328 times
It described the ripping tooth (top half of the picture) as being the same as a kannami (plane blade), while the cross-cut tooth (lower half of the picture) is said to be akin to a (marking) knife slicing across the fibers - he used the term kogatana (小刀). I can see his argument for a negative rake tooth pattern for cross-cutting.

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