Chris Schwarz's Blog

Western Teeth, Eastern Teeth and a Greek Salad

Between bites of salad, Kevin Drake pauses to take a close look at the common chair sitting in our local Panera.
 
When I look at the chair, all I see is your typical bent-lamination, factory-made, comfortable-for-about-32-minutes padded chair.
 
But Kevin, the founder of Glen-Drake Toolworks, sees a lesson in Japanese aesthetics and composition by Japanese arts teacher Shozo Sato. What is the dominant focus for the viewer? What is the sub-dominant; the subordinate?

I was chewing my food at the beginning of the explanation, but by the end I was listening so intently that I forgot about the baguette soaking in my own mouth juices as I finally “saw” the chair.

Nothing makes me happier than to have lunch with someone whose brain is on fire with ideas different than mine. Someone who sees the same world with different eyes.

Which brings us to handsaws.

It’s a common thing to read in woodworking texts that the ripping teeth in a Western saw (power- or hand-driven) are shaped like chisels. And that crosscutting teeth are shaped like knives.

But when Kevin sees sawteeth, he sees something different. He sees the function of the teeth relating more to its “rake,” which is how forward or backwards each sawtooth leans. On a handsaw, teeth with the cutting face straight up have “zero rake.” Teeth that lean forward into the cut have a more aggressive rake. And teeth that lean backward have a relaxed rake. (Whether the rake is “postive” or “negative” depends on whether it’s a power tool or hand tool user describing it.)
 
To Kevin, Western ripping teeth don’t look like chisels; they look like scrapers. Scrapers attack the work in an almost vertical position , like a zero-rake sawtooth. I can see this (see the photo at the top of this entry of a wooden model of Western sawteeth).
 
And to Kevin, it’s the Japanese-style sawteeth (shown above right) that look like chisels. They lean forward like a chisel being used for paring. And I can see this, too.
 
So Kevin then asks three questions:
 
1. What type of wood scrapes better, hardwoods or softwoods? Easy. The harder the wood, the easier it scrapes.
 
2. In general, which woods are harder, Japanese woods or Western woods? Again, it’s an easy question. Western woods are harder.
 
3. When you scrape a wood, is it easier to push the tool or pull it? You can do it both ways, but I definitely prefer to push the tool.
 
“That,” Kevin says, “is why I prefer Western push-style saws.”
 
That statement was like a Zen Buddhist riddle (called a koan) for me. Thanks Kevin. Now I’ll never look at my saws (or the Panera chairs) in the same way ever again.
 
– Christopher Schwarz

P.S. This coming week (May 19 to 23) I’ll be teaching at the Marc Adams School of Woodworking, so there won’t be many (if any) updates to the blog. Enjoy your vacation!

6 thoughts on “Western Teeth, Eastern Teeth and a Greek Salad

  1. Ray Gardiner

    I understand the argument with respect to rake, what I think is not clear is that with a scraper you are pushing parallel to the grain not the same as sawing, where the angle of the teeth is anything but parallel. You can get pretty much any cutting angle you like by tilting the blade. Which is why those old books show the first cut at a fairly shallow angle when starting the cut, and much steeper (guessing here, but closer to 30 deg from vertical) I am talking rip here of course. Refer to "The Practical Woodworker" Bernard E Jones pages 50-53. For short boards, held vertically in a vise. Like cutting tenons or dovetails he shows the blade flat. Seems contradictory if the teeth are filed the same. Either way, as far as the scraper analogy is concerned if it’s a scraping action, then you are scraping end-grain.

  2. Carl Stammerjohn

    I have come to a little different conclusion regarding the rake of Western vs. Japanese saws. I think they are effectively very similar, even though the geometry at the tooth is different. I say "at the tooth" because the situation is different if you look at the saws when they are in use.

    Imagine a line drawn from the handle on a Western saw through the teeth. The line roughly intersects the cutting edge at about 90 degrees. Do the same on a Japanese saw; because the teeth are facing the other direction, you get a similar result. The "effective" rake of both saws is actually much closer than it would appear if you looked solely at the tooth geometry.

    Both types of saws are using their teeth as scrapers; they would be far too aggressive if their effective rake was positive.

  3. Rob Porcaro

    Push, pull. Tails first, pins first. Mac, Windows.

    I very much appreciate discovering the rationale behind different approaches to getting a job done and the subtleties of tools. However, I think there’s a simple fact that often gets lost in many of these discussions: there is more than one good way to accomplish most tasks!

    Some birds crack nuts with their beaks, some birds eat worms, and I crack open nuts with a nutcracker (and never eat worms).

    Rarely does one method hold all the advantages. But all useful methods must have clear rationales and have gone through evolutions with discovery and preservation of the nuances that make them work.

    Chinese or Italian? It’s good eatin that counts.

  4. Christopher Schwarz

    Ben,

    Western planes and cabinet scrapers can be pulled, but their grips are designed for pushing. So I think the design drives that preference more than anything else.

    I think the preference for pushing a saw has more to do with the tooth shape. The Eastern rip tooth is generally set for a more aggressive action that is ideal for softwoods (and too grabby for hardwoods). The Western rip tooth is less aggressive but is ideal for hardwoods (but slow for softwoods).

    As to pushing and pulling a scraper, who knows? You can do it both ways, but pushing seems more effective for a variety of reasons. Perhaps what is the defining factor here is what is missing from the equation. Pullsaws are effective because you can keep the blade in tension by the act of sawing. The scraper doesn’t have this advantage on the pullstroke.

    Chris

  5. Ben

    Since this whole thing is in the vein of philosophy, I want to understand one point.

    When discussing push/pull, the notion was that pushing is preferred with "a scraper". If it’s a hand-scraper, then pushing preference seems most likely a byproduct of our hand shape. If it’s a cabinet scraper or a scraper plane, then it feels like it could be a question of "what you’re used to", i.e., most westerners learn on push planes.

    So, is this a fair analysis of why a push saw is more sensible? Or is it confirmation that we like what we know? Just curious for your thoughts 😉

    -ben

  6. Wilbur Pan

    Thanks for a great explanation of this. I never completely understood how the rake interacted with the type of wood being cut.

    It’s been known for a long time that Japanese saws can be set up to have teeth optimized for hardwoods as well as softwoods. In this case, the rip teeth are set up exactly the same as the picture of the model of western sawteeth: with a zero or slightly positive rake. There’s a picture of this in the chapter on saws in Toshio Odate’s book on Japanese tools.

    In fact, the people who sharpened Japanese saws (metate) would adjust the rake on the saw they were sharpening to optimize it for the type of wood to be sawn, and so Japanese woodworkers would have their hardwood saw and softwood saw.

    Currently, there are Japanese saws with disposable blades that you can buy that are identified as "hardwood" Japanese saws. These blades have rip teeth with a less aggressive rake than what you would find on a standard Japanese saw. I have one of these saws, and it looks like the rake is about -2 degrees. This is still more aggressive than the rip teeth of a typical western saw, but certainly less aggressive than a Japanese saw set up for softwoods. (There’s also other stuff going on with my saw– the rip teeth are not true rip teeth, as they have a small facet filed at the very tip of the tooth to make it a little like a crosscut tooth.)

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