Tuesday, September 23, 2014

The Saw Club

The first rule of saw club is you don't blog about saw club.

The second rule of saw club is saws are either hanging or in use.

The third rule of saw club is japanese cross cut are filed with a large slope.

First two rules must be obvious, but the third seems not to be so widely acknowledged. (And here you will meet the part of my personality that Austrian seem to hate the most. If I see something wrong I will point to it and just say it, and show you with facts why you are wrong. Call it professional deformation, but I do think that right and wrong exists, and furthermore, there are pretty easy to differentiate.)

So, our good old Wilbur is doing it wrong:

While this young man is doing it right:

Can you see the difference?

Let me tell you how I came to this realisation. I've been looking at getting a nice zaagklem from markplaats for some time now. But because of the weight I haven't been so convinced to pull the trigger.  Besides, having the saw vertical is not the most comfortable way to file for me, since like that the file is always pointing up... wait a minute, I said to myself, that's why this japan guys like so much to work sitting.  If you put the saw at an angle, then you can file straight (which seems to be easier — I would say that we are biologically wired to recognise the horizontal, and not, say, 17.45 degrees... at least it makes sense to me from an evolutionary point of view. Anyway, back to filing. )

So why haven't anyone talked about this? No idea.

But the idea is not new, it even seem to have been normal here in the western world in the wood old times, good old times — pardon me, I have a problem pronouncing the "w":

Does it look familiar? Yes indeed, the guy from the drawing is half japanese. (Btw, go to the source and read the article, it's well worth it. And I am SOOO much scanning my saws, I hope nobody thinks I'm crazy here in the office.)

What's the problem with filing without slope then? You cut on the back of the teeth with the file. I have some steel from scrapers Julia bought to spread butter on the walls, or something like that, that I can use to show the different slope side by side (and they may be easier to scan also).

(Good news, I can save the money from the saw vice and buy more files. Actually, I think this make the gramercy vice useless for me, so I just saved 180 euros, that's plenty of files.)

Now for a bit of geometry. Hope you had good marks in trigonometry at the university otherwise skip to the end of the post and I tell you how to do it with hand tools.

Indeed, conic sections. It has everything to do with saw filling, I'm telling you.

If you intersect a plane with a cone, you will get different shapes depending on how the plane is oriented with respect to the axis of the cone (cf. wiki page on conic sections):

Well, your plane is the saw blade, and your solid is the file. And when you sharpen you intersect them, so depending on the angle at which you intersect them, you get different geometries. And cutting wood is all about the geometry of the steel, isn't it?

I'm not very good at 3D imagining, but I hope you catch the drift with the following pictures.

First, no fleam and no slope, like a rip tooth.

Here, the file is transparent yellow, so you can see the cut it makes on the steel plate. Blue paper steel, of course. 

Then we add a bit of fleam. We are moving the blade and not the file, and you see that the geometry changes, but it still looks like a western tooth. 

But now, we add also a slope, just like the old japanese guy from the video, inclining the saw blade. 

Now we are there. If you look close to the intersection of the saw and the file, the angle of it has changed, plus, the gullet is deeper.

Just repeat at a fixed interval and you get a saw.

I hope you are convinced now. The third rule of the saw club is japanese cross cut are filed with a large slope.

P.S. The hand tools way to do it is to plane a "wooden file" and cut it at different angles, this way you can see the effect of fleam and slope directly just by changing the plane at which you cut your "wooden file". I will do it as soon as I go home, sadly I ran out of saws and scrap wood at the office.

EDIT: I found the picture I was looking for. Here you can see clearly the large slope Nagakatsu-san uses

And I don't know hoe goed jou nederlands is, maar hier kan jij ook een lekker filmtje kieken in de keuken. https://www.youtube.com/watch?v=4j5B6C0m15E


  1. Excellent work here! I commend Wilbur for addressing this topic, and showing many people that there is nothing to be feared, even for beginners like me. That said, his approach is a beginning. What you are showing is leading us down a longer, and possibly darker path, haha! What you are saying is correct, though. The angle of presentation will effect the shape of the tooth, and the angle helps determine the tooth profile. An acute presentation results in a tall tooth with deep gullets.

    When filing perpendicular to the saw blade (disclaimer: my experience here is slight, and on western saws, at that) you are..... you are.... Well, it just feels unpleasant. Like you are fighting the nature of things. Angled feels easier on the saw blade, and on the file, too.

    I suspect that using the angled saw vise allows for a smoother run of the file. This would translate into a more refined edge to the tooth. Think of the pattern that the file leaves on the filed surface. A purely horizontal/ linear stroke leaves an undulate textured surface, but when draw-filing the surface looks much different, a finer texture. This simple thing (an angle saw vise) might actually be one of the "big" things that contributes to a saw that performs really well. The vise helps with those last, delicate passes of the file that leave a superlative edge, one without distortion or ragged trauma, perfect and smooth.

    I love that file-holder thingy that the metate uses.


    1. Indeed, I am heavily indebted to Wilbur for showing us the path... But in my world the best form of flattering is ruthless criticism :P

      Exactly, it goes against the grain to file with no slope.

      The small little thinky that I fink funky is another simple "big" thing. Think of the rope walkers. They use really long sticks to help keep the balance. with a longer file, is easier to detect the angle movements, and this results in more precise bevel, and thus a better cutting.

      It's another thing on the to do/to post list, but I wanted to keep it under the arm till is done. You too fast tho, I guess I will have to try to make one out of wood. Wait. I think tomorrow I can drop by the workshop of the uni and see if I find something suitable.... let's see

  2. Perhaps it is my Moon in Pisces, or it may be my respect for your strength of intention, but I am reluctant to say this is wrong.

    Still, this is not the way I do it. How it was taught:

    Sit on thin pad, hold vise with legs, elbows on knees, vise leaning on box within which, fileings fall. I've heard it said this crossleg position "opens the heart" whatever work you're doing.

    Feather file perpendicular to blade, rip and crosscut. Various size saws need proportional size feather file. this makes a flat bottom gullet which can be made uniformly deep from end to end, which means regulating the teeth can be quite precise. The back of single sided files reflects through a very small gap, the adjacent x-cut tooth. This reflection indicates extreme small deviation in angle. Between this reflection, the size of the top jointed surface, and the distance between the top of the vise and the gullet bottom, the sound of the file, these are all you need to guide you. After a while, your breathing is even and flows through your body into the saw, from hara to hara. Steel will remember your energy for a revolution round the Sun. Sometimes longer.

    Set of teeth and straight and flat blade are crucial to a straight cut.

    Sane work leads to a sane life.

    Satisfying work leads to a satisfying life.

    Know the local universe through your hands. (Ahhh! - it's good!)

    1. Thanks a lot Mark, this is gold.

      The filing has been evolving, and elbows on the knees became the preferred position and the slope will depend on the saw I'm working. I'm trying to repeat the geometry the previous metate put on it (and adding some chumasaru rake too.)

      I need to get a single sided file, I have none but I can totally picture what you say.

      To sit, I'm using a piece of felt my wife made, it's nice to have warm feet on winter.

      Set I think I got the hand of it, but straightening the blades... that needs plenty of work still. I'm thinking of forging my own saws so I can understand first hand the dance of the hammer and the steel.

      Feynman said once that all you need to learn physics was a candle. Some days I surprise myself looking at the same blade for hours... it feels like home. A little piece of the world that is a world in itself.

      What about the thickness of the blade? I imagine the set needs to be constant along the length of the saw but in several cheap/old/machine made saws I have this is not the case. So I'm filling them down to constant thickness and it has worked quite well.

      And on the same topic, filing only the facets is not like sharpening only the bevel side of your kanna? You should also touch the "mirror" side once in a while, isn't it?

      Sincerely thanks for your advice Mark

  3. Also, if the saw is tipped away from you, how could you see the top jointed surface?

    1. You don't. I guess that looking at the gullets and knowing that the angle of the file was constant, you can infer it. But that's just my guess.

      What I do is to go slowly and check after a few complete passes how the saw looks. Then I may file the third facet and give it a try. Sometimes it works, sometimes needs more filing.