I went down to the crosscut roads: Japanese saw sharpening — III
Now that the rip side of my 270 mm ryoba has been sharpened, that leaves the crosscut side, or, as it’s more commonly known, “The saw teeth that no mere mortal woodworker dare touch”. In fact, although sharpening Japanese crosscut teeth is more involved than western crosscut teeth, I don’t think that doing so is impossible. Disclaimer: I have no idea how close this method is to historical practice, but it does seem to work well for me.
The key for me was realizing that the main difference between Japanese crosscut teeth and western crosscut teeth was the third facet at the tip of the teeth.
This isn’t news, of course, but take the facets away, and what is left are basically tall skinny western crosscut teeth that lean to the right.
There is a post with a more complete illustration of how western crosscut teeth can be transformed into Japanese crosscut teeth.
My approach is to ignore the third facet at first, and pretend that all I am doing is sharpening tall skinny crosscut teeth with an aggressive rake. I start by jointing the teeth with a file.
You can easily see the flats left by the file.
Next is to file the leading edge of the teeth that are leaning away from me. Like western crosscut teeth, I’m working on half the teeth at one time. I use the same diamond shaped file that I used to sharpen the rip side of this saw. The angle gauge is to help me maintain a constant angle for the fleam. I’m going for 15º here. This saw seemed to be set up more for softwoods when I got it. The fleam angle was greater, which left a more knife-like bevel on the teeth. I picked 15º because I wanted this saw to be tuned more for hardwoods, and well-known Japanese saw aficionado Ron Herman said that 15º was a good fleam angle for hardwoods on his sharpening DVD.
After finishing filing the leading edge, I file the back edge, also going for 15º.
Then, the ryoba is turned around in the saw vise, and the same process is done on the other half of the teeth. Up to this point, the sharpening process is pretty much identical to sharpening western crosscut teeth, and in fact if this was a western crosscut saw, I would be done at this point.
But we have that third facet at the tip of the sawtooth to deal with. Filing the facet is really much simpler than the conventional wisdom holds, however. In order to do this, I just angle the file so that it’s pointing slightly upward and towards the leading side of the sawtooth, and establish a facet. Like the initial filing of the crosscut teeth, I’m working on half the teeth, the ones leaning away from me. Because the tip of the sawtooth is so small, it only takes 1-2 strokes of the file to establish the facet. This process should also make the flat made by jointing the saw at the beginning of this process disappear.
This is where the safe edge of the file is important. It’s very hard to make this filing stroke without touching the adjacent sawtooth. The safe edge minimizes the damage done to the adjacent sawtooth. Even so, the file can put a small nick in the tooth if too much pressure is applied. Although the file has a safe edge, it still is harder than the metal used to make the ryoba, and because the diamond comes to such an acute point, a lot of pressure can be generated with little effort.
There is probably an ideal angle to use for this facet, but since I want to use this saw on hardwoods, I shot for angling the file up about 15º from horizontal, in keeping with Ron Herman’s fleam angle advice. In general, the harder the wood, the less of a facet you want. For softwoods, the file would be angled a little further down from horizontal, and a longer facet is made.
After finishing this, flip the saw around, and repeat the process on the other half of the teeth, and that’s it. You’re done.
Again, I have no idea as to the historical accuracy of this method, and I fully realize I haven’t even tried to address the issue of set. But this method seems to work well, as can be seen in the photo from yesterday.
Tommy McClennan, Cross Cut Saw Blues:
I cut your wood so easy,
You can’t help but say, “Hot Dog!”
Crosscut in a scrap piece of 8/4 cherry with a 270 mm ryoba with freshly sharpened crosscut teeth.
Yes, sharpening Japanese crosscut teeth can be done.
Filing the rip teeth on a Japanese saw is pretty straightforward. Altogether, it took me less than 3 minutes to complete the filing of this saw.
This video is worth 2.2 million words.
Q:Great post Wilbur,I can't wait until your book comes out ; ] Where did you source the Japanese file?
Thanks! Although I highly doubt a book is in the cards.
To be honest, I don’t remember where I got the file from. I’m pretty sure it was from Lee Valley. There are a surprising number of sources for Japanese saw files, including Hida Tool, Japan Woodworker, Tools for Working Wood, Woodcraft, and eBay, of course.
Rip this joint: Japanese saw sharpening — II
One of the areas of woodworking that still fills many woodworkers with dread is saw sharpening, and the idea of sharpening a Japanese saw seems almost incomprehensible to woodworkers all over. But sharpening a Japanese saw may not be as weird as it may seem.
Please note: I’m not going to even pretend that I’m some sort of Japanese saw sharpening expert, or that I’ve become a metate guru. But I think I have figured out a straightforward approach to sharpening Japanese saws, and as I hope will be clear, a lot of this is based on the approach used to sharpen western saws.
This is an old, sad, 270 mm ryoba that I picked up from eBay a while back. Its primary attraction to me was that it was cheap. This is the equivalent of a rusty old Disston that you might find at a garage sale for a couple of bucks, except that this ryoba doesn’t even have the equivalent of the Disston name.
This ryoba seems to have been set up for sawing softwoods. The rake on the rip teeth is pretty aggressive.
The crosscut teeth are on the tall and skinny side, and the third facet at the tip of each tooth is a bit long, which is what you see with Japanese crosscut saws that are optimized for softwoods.
Just like western saws, Japanese saws need to be held in place for sharpening. Toshio Odate has a diagram of a shop-made wooden saw vise in his book. As it turns out, just prior to the October 2009 Woodworking in America, Tools for Working Wood had just come out with the Gramercy Tools saw vise. I had asked Joel Moskowitz whether the Gramercy Tools saw vise could be used with Japanese saws. He said, “I don’t know. Bring one along and we’ll find out.”
As it turns out, it does a fantastic job of holding a Japanese saw.
I started on the rip side of the ryoba. The first thing I did in rehabbing this saw was to joint the tips of the rip teeth. To do this, I used a mill file to go over the tops of the teeth.
By doing this, I level the tops of the rip teeth. When there’s a small flat on the top of all the teeth, I’m done. Some of the teeth were sticking up a bit more than the others, so after the jointing process was finished, the flats left on those teeth are larger than the others.
Now it’s time to file. The files used for Japanese saws are different from the triangular files used for sharpening western saws. Japanese saw files have a very narrow diamond profile, and are sized for the length of the saw that they sharpen. Larger files are used to sharpen larger saws. Also, on this file the edge at the acute corners are rounded so that they cannot cut metal. This is to prevent nicking the adjacent teeth when working on the tip of the crosscut teeth.
There are Japanese saw files that do cut at the acute corner. I need to get some of these eventually, as this is the sort of file that would be used to deepen the gullet. I don’t need such a file for this job, as all I’m trying to do is get this saw into working order.
Filing the saw is straightforward. I keep the file at 90º to the blade. The thinness of the file makes it easy to see the angle. Then I file the cutting edge until the flat disappears. Here’s where the relative thinness of a Japanese saw really comes in handy. The flats disappear after just a few strokes. Even on the large flats, it only takes about 30 seconds to sharpen that particular tooth.
For this particular ryoba, I want to alter the tooth geometry so that it is more optimal for hardwoods. To do this, I’m relaxing the rake angle a little. I’m not trying to reshape the entire cutting face of the tooth. Instead, I’m reshaping the tip of the tooth so that that part of the tooth has a more relaxed rake angle. The majority of the tooth face is untouched. The overall effect is sort of like putting a micro bevel on a plane blade or chisel. Of course, if this saw was already set up the way that I wanted it to be, I’d be filing the entire face of the tooth.
It’s a bit hard to photograph the effect with the camera that I have, but you may be able to see the altered rake angle in some of the rip teeth in this photo, especially in the third and fourth teeth from the left, and the second whole tooth in from the right. As this saw gets resharpened in the future, the cutting face of each tooth will become more even.
Finally, I take a pass or two with the file on the other face of each tooth. This takes very little time.
So how did I do? This saw certainly cuts better than before. Here’s a quick cut I made in a scrap piece of 8/4 cherry.
The cut face isn’t perfectly smooth, but it’s surprisingly good overall. The saw cut very quickly, and was certainly an improvement from when I first got it. The saw could use some tuning up of its set, which I haven’t tried to do on a Japanese saw yet. I plan to run a waterstone or a file down the sides of the teeth to even out the set, like you would do on a western saw.
As I mentioned above, I would argue that this method of sharpening Japanese rip saw teeth is almost identical to how you would sharpen a western rip saw. Ron Herman, the well-known Japanese saw aficionado, recently came out with an excellent DVD on saw sharpening, and his procedure is nearly identical to what I illustrated here: joint the teeth, file the front face until the flats disappear, then briefly work on the back side.
Now for the crosscut side. Stay tuned.
Kissing cousins, redux
I wasn’t happy with the mockups that I originally used for this post, so I finally got around to making a new set of mockups that I like a lot better, and used them to reshoot the photos. Please take a look. I think the new photos better illustrate the connections between Japanese and western crosscut saw teeth.
Kissing cousins: Japanese saw sharpening — I
It’s often said that the angles on Japanese crosscut sawteeth are complicated and confusing. I think that they don’t have to be. There is that third facet that is characteristic of Japanese crosscut sawteeth that doesn’t really exist in western saws, but if you temporarily ignore it, it’s easy to see where the three facets of a Japanese crosscut sawtooth fit in.
Here’s a mockup of crosscut sawteeth on a western saw (with apologies to well-known Japanese saw aficionado Ron Herman).
Now make them tall and skinny, which increases the volume of the gullet. This is a good thing, as it means that there’s more room in the gullet for sawdust to go, which helps keep the saw from clogging.
From a topographic standpoint, there’s really no difference between the crosscut teeth of a western saw and this mockup.
Now let’s lean the saw teeth to the right a little.
Now we can slice off the top of the sawtooth.
This is very close to what a Japanese crosscut sawtooth looks like. Since the teeth are leaning to the right, that’s where the handle would be, and the saw would be pulled to the right to make the cut.
UPDATE: I wasn’t happy with the mockups that I originally used for this post, so I finally got around to making a new set of mockups that I like a lot better, and used them to reshoot the photos.
