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
Groets