Some thoughts on sharpening Japanese saws– It's the little things

 

Lately I've been waking up in the morning and *reeeaaly* wishing that more people were writing about sharpening saws, Japanese saws in particular. I guess that I'm just obsessed, but saws have been in my mind for a while now, and I just can't get enough. 3 o'clock in the morning, and I'm wondering if it's too early to get out of bed and get back to work, sharpening more saws.

 

Yeah.....better not. It's too dark to see, anyways. Have I mentioned that we don't have electricity?

 

 

 

Almost nobody writes about this stuff, not even in the Japanese blogs. Sebastian has been doing a great job resurrecting the sharpening art, and Gabe is doing wonderfully with his big Maebiki-oga's, but.....I want more. What little I find amounts to :

• Here is a diagram of a rip tooth. Copy it.
• Here is a diagram of a crosscut tooth. Copy it.

 

 

 

 

 

The truth of it is that those directives are absolutely correct, and as a beginner, there is no better way. Look at what a "proper" tooth shape is, then emulate. When your saw starts to behave strangely, it's probably not your imagination, because they do get dull. Just because your saw is a superawesome Japanese tool, well.....it's just steel. Before it gets too dull and something nasty happens, point that bugger up. Freshen up those facets, it's not that hard. If your saw isn't too messed up, you merely copy what's already there. It's easy (almost). Assuming that you've got a decent, non-impulse hardened tooth saw....and a file.

 

 

 

Sebastian, Mark Grable and I went in on buying a Yahoo Japan auction lot of saw files, bought and shipped through the excellent kindness of R-K Trading Company (thank you, Murakami!). I'll tell you this....I'm never paying retail again! Admittedly, it seems like we did get a bit lucky, we got them so cheaply. I wish that we had bid on the other lots as well, but in any event, I now have an embarrassment of 75mm, standard cut, double edged yasuri feather files.

 

 

From what I've been able to determine, Japanese saw files come in a standard cut and a finer cut (called "aburame"). If you take two files, one standard and one aburame and place them side by side, you will see that not only does the aburame have a much finer tooth spacing, it also has a thinner cross-sectional shape. These particular 75mm files are almost a perfect cross-sectional match to my fine tooth aburame 125mm file, despite its being almost twice the size. All of these files are incredibly narrow, delicate creatures, but comparatively speaking, these 75mm files are bruisers.

 

These files are all NOS from an old hardware store or something, Tsubohi File Works and Co., God only knows how old....50 years? These files leave a relatively coarse finish to the saw teeth, not exactly what you'd want for a final sharpening. I've been sharpening every saw within reach, and so far I'm still using the first one that I pulled out of the box, so I would say that these Tsubohi files are both forgiving and VERY durable. What the hell am I going to do with the rest of the 4 boxes.....I need more saws, obviously!

 

Japanese yasuri saw files come double sided, as these are, and single sided fine cut, a seemingly rare beast. 80-90% of the files that I see at auction are the standard double sided, and this must be indicative of something. I see two immediate possibilities. Assuming that 50 years ago the manufacturer made an equivalent number of all types of saw files, we can see that everyone loved the fine tooth single sided files so much, that they used them all up. All that are left now are the sucky, hated, standard double sided files.

 

Or....

 

Standard tooth, double sided files were made in far greater numbers because they are such useful creatures and were used for such important tasks, that the stores needed to keep their shelves well stocked. I don't know, I'm just guessing, but I'm thinking that these files have a specific purpose.....and the fun is in the finding, no?

 

 

All this talk about files, but they are actually only peripheral today. Today is about the forgotten side of the tooth, the actual "side" of the saw.

 

 

I was working on a saw the other day and I took some pictures to get a better look at things.

 

 

 

Not horrible (aside from the gullets being sloped the wrong way....too much island bliss, I guess), but when I look closely at the "dark" side of the tooth facing the camera, I see little specks of light. Those specks will be tiny jagged areas, perfect for snagging stray wood fibers and clogging the action of the saw.

 

 

A few of us have been pestering Mark Grable mercilessly for tips and information, anything Japanese saw related, and he's been wonderfully forthcoming with his knowledge and experience. Often, the briefest statement will have broad influence, importance far in excess of its brevity. Nerdy though it is, I've got a document of "Grable'isms" that I read before working on a saw, and it's amazing how something that you've read a thousand times before, will suddenly being new insight into a problem you are having. Case in point, Mark has mentioned that it's difficult to know what you are seeing, if the saw is all dark and pitted with rust.

 

What?! Rusty saws?!

 

Being attracted to the old and neglected, all my saws are rusty to varying degrees. Check out these treasures.

 

 

The little rip kataba in the center you might remember as being the subject of an aborted series on saw rehab I never brought to completion. I may have "massaged" the poor thing to death, just as you can soften metal by using a planishing wheel. The narrow bladed saw just to the right of the kataba has become one of my favorites, though. Ugly, rusty little thing, but it's a handy blade shape for pruning and trimming green wood.

 

I've already sharpened this a couple of times –I'm currently sharpening the saws at the merest HINT of being dull–, but then I started thinking about the side of the saw tooth. This is the equivalent of the "back" of a plane blade. You can't get a plane iron sharp if you only sharpen the face and ignore the back.

 

Duh!

 

The simple solution to the problem is....well...I don't know.

 

Ignore please, my use of a file here.

 

What I am really doing is gently scraping any trace of surface rust from the sides of the teeth that are facing toward me. I'm using the forward edge of the file as a scraper because it is easily the hardest steel that I've got handy. Really handy, like, already in my hand, haha.

 

 

And for Sebastian.....This is the saw that I mentioned in you comments regarding your universal dozuki. It was originally a purely perpendicular tooth rip pattern, with all teeth being the same size. I gave it more of a short and fat crosscut shape, with a stubby top facet. I'm putting together a post on my experiments with varying tooth geometries, but it might be a little while before things slow down some.

 

This saw, like most others, has teeth with a slight set, so the teeth are slightly bent to a curve, not straight. To polish the side of the tooth requires a curved implement of some sort. I tried using a curved/rounded edge wooden block with some #220 sandpaper wrapped around it. A flat sanding block will just level out the sides of the teeth, leaving you a saw with no set. Binds-ville, man, Binds-ville.

 

 

It works, and if that's all you got, use it. It's a pain though, and the tendency of the sandpaper is to round over the edges of the teeth. That's bad obviously, so try to find something better.

 

 

Much better for me, was a little Washita sharpening stone with a radiused edge. Different saw, but the idea remains.

 

 

Hey! My saw grew another set of teeth! A synthetic stone was too soft for polishing the edges of the saw teeth. An Norton medium India slipstone would be perfect.

 

 

Edit: Added a pic Here.

 

Here you can get an idea of the polishing effect at the tops of the teeth, although these are far from perfect. Remember, only the teeth that are facing upward are being polished. The ones that face away don't matter. Small steps, incremental change.

 

 

More than anything though, this really seems to point out how skilled you are in setting the teeth, because every discrepancy leaps right out at you. It's a good opportunity to even things up, work on your Asari skills.

 

 

 

 

Of course, once I got started.....

 

 

The dark red stone next to the soap is a small offcut of a synthetic #1200 waterstone. I takes a few swipes with that first, to seed the surface with abrasive grit, then do the bulk of the rubbing using the much slower natural stone.

 

This revealed lots of lumps and bumps.....Oh boy!!!

 

 

 

Off to the anvil, just give me an excuse, any excuse.

 

 

The lighter spots are deviations from the average plane of the saw. Lumps. They aren't bad though, so my little tack hammer seems the proper tool. Many small strikes, focusing on the areas around the bumps more than the bumps themselves.

 

 

My point here, assuming that there is one, is that the smallest things can have large effects. The teeth of your saw will never be truly sharp unless the sides of the saw blade are clean and smoothly polished. A little bit at a time, if your saw looks as bad as most of mine. If I were to get the blade to a polished state, most of my teeth would be gone, abraded away in the process. Better is to sneak up on polished, taking a little off at each sharpening, so the edges get incrementally improved. With just a slight amount of work, I've probably made the saw 30% sharper, although cleaning and working the sides of the teeth actually dulled them a bit, so some touch up was required.

 

The big ryoba worked fine with those little bumps and dents along the blade, but as with the rust, it is better to have as straight a blade as possible. Less friction, and it's fun to hit things with hammers.

 

It's the little stuff, dontcha know.

 

 

Oh boy....it's finally getting light out. Time to sharpen something!

 

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Correcting a "chippy" blade...

I've got this great little kanna blade, 48mm wide and I use it all of the time. It has one significant problem, however. Try though I might, the edge develops little micro-serrations in some areas, and don't want to come out, no matter how much I sharpen.

There is a procedure called "Killing the edge" that often works to correct for this jagged edge tendency. When it is time to re-sharpen, you first drag the edge over something hard. A glass works nicely but the side of your sharpening stone works well, too. What you are looking for is a clear, unbroken line of "bright" that runs the full length of the edge. This line of clean metal ensures that you are into the fresh stuff, and not fighting some remnant scratch or blemish.



Some blades are difficult no matter what you do.


Right now at least, I prefer very hard blades. Sometimes the blade can be TOO hard, though. I suspect that the degree of hardness that the blade is capable of carrying is partially due to the underlying grain structure of the steel. A fine grain structure will support a very hard edge, where a more coarse grain will tend to chip or fracture. The grain of the steel is established by the blacksmith, so we are stuck with that, being what it is.

A coarse grain structure needs be softer, in order to maintain its integrity. Tempering is the act of softening a blade, and is something that is well within the abilities of anyone. Easy stuff.

Really.



Preheat the oven (I start at 325°F).

****
Preheat the oven, because your oven runs full-bore until it reaches operating temperature. The high heat would potentially harm the blade, so.... Preheat.
****

Place the blade on something large and heavy/dense.

Some ovens control their heat more accurately than others, and the cast iron skillet (in this case) acts as a buffer. A little extra protection (and I was seasoning the skillet anyways, so I got to kill two birds with one stone!).

I cook the blade for 30-60 minutes. The actual tempering occurs nearly instantaneously, but extra time won't hurt anything and may contribute to a more thorough temper.


After the blade is done cooking, let it cool, then back to the stones.

Not good enough. 325°F didn't seem to change a thing.

Magnification concurs. The jagged edge remains.



So, back into the oven, this time at 350°F for another 30 minutes, then sharpen.


Better, so at least I might be on the right track, but not good enough yet.


I try again at 375°F...

Much better, smooth and straight. I don't want the blade any softer than necessary, so I'll stop here, for now.

This blades jagged tendencies appear to have vanished, but I'll reserve judgment for now.


The blade seems to sharpen up much better now, both easier and "sharper" feeling.

The kanna works better. Nothing to write home about, but definitely good performance. The true test will be in the longevity and ease of re-sharpening.



I could possibly get more work done if my assistant would stop napping on the tools, though.

I was taking a break from all of the carpentry obligations of the last month, by spending a little time in front of the forge (Yay!!!! Hammer time!!!). I am trying to salvage a sloppy laminated blade that I forged a few months ago. After a lot of massaging, I've ended up with something that is getting close to being a proper blade.

The heavy lifting in the shaping department has been taken up by the $Store sharpening stone. This is proving to be a favorite of mine, being soft enough to function as a waterstone, but hard enough to hold its shape without immediately dishing. And it cuts fast! Amazing performance for $1!


I only tempered this blade to 325°F , and it's WAY too hard for a kitchen knife. Harder than anything that I've ever used before, anyway.

Even worse..... Chipping at the edge.

I tried a second temper at 350°F, and it might have been sightly better, but still chipped pretty bad.


So.... I skipped right to 400°F.

375°F would've been perfect, haha! 20/20...

400°F didn't ruin it by any means, I just like to be more thorough about these things. You don't learn as much if you skip the proper steps, you know?



Unfortunately, this blade is a junker.

This little crack will propagate. I could take in the edge a bit.... Regrind the bevel...


The tip would need some work too. See how the end looks all fuzzy?

That's because the hard steel runs out and gets mixed in with the soft iron. The tip is too soft. The "fuzziness" is due to the way that the iron finished on the natural waterstone. The hard steel finishes to a near-mirror state. I could grind the tip back until I get to the better steel......


Even though the steel is now soft enough to *barely* form a burr, it still tends to chip out.

*hmmm*

I don't want to temper the blade any higher. It's soft enough already (actually it's a very practical, hard edge. I just want to see *how* hard I can make a knife!)....I am wondering if I could improve the steel structure through a series normalizing/grain reduction heats, at the forge, and do a new quench...... Re-shape the blade...... Sharpen again......

The new blade would only be, ohhhh.....a paring knife maybe?

I've already spent an unreasonable amount of time grinding out that uber-hard bastard, what's another hour?

Good practice.

Chisel rehab/therapy

I guess that I've been restoring too many of these old tools. I've noticed that periodically, when I'm getting a bit restless and notice a sort of itchy feeling..... It's time to sharpen something. Today feels like a chisel day.


Buying old chisels that haven't seen much action, then getting them ready for use, has turned into a favorite form of relaxation for me. If they haven't been used, they haven't been mucked up, most likely. This makes for a fast and fun(?) setup.


Junji sold me this nice old 36mm Toyohisa chisel. I set this guy up a few days ago.

There isn't much to show here, really. These chisels required..... not much. A good cleaning with a cleaner/degreaser (409 works well, and won't dissolve your skin, haha!), followed by a scrub with #0000 steel wool removes all of the grime and light oxidation. I have shown those processes often enough that I thought to spare you the details (or just forgot to take photos?).

On probably 75% of the chisels that I buy, I need to drive the chisel hoop (the kasura) further down on the handle . This chisel was no exception.

 I put shellac on my tools to keep them looking somewhat clean. Shellac, varnish, and polyurethane (I draw the line here) are all film forming finishes, and might not be the best choice for tools that get handled much. Oil finishes might be better, but they tend to go black over time, and often get sticky as well. Shellac is quick to apply, easy to renew, and simple to remove. I would prefer the handles to stay unfinished, but they get so nasty looking..... Vanity wins!



The ura side of this chisel was in really good (original) condition, so I get to shape things as I wish. Establishing and maintaining a nice shape to the urasuki is part of the fun for me.

Wow, I need to get a life, haha!


This is a high quality, older chisel. It has the stamp of the Tokyo chisel makers union, long since disbanded.

This is a 9mm by the same maker.

The ura side is looking nice. The better quality tools often are easier to setup, this being no exception.

Part of what I find so enjoyable about the initial setup, is that you are obligated to do your best work because the results will be visible for the life of the tool. The ideal isn't to do this as quickly as possible, but to do your best.


The bevel is not done yet..... saving some fun for another day.

A small chisel, short (6.5 inches, more or less) and narrow (3mm).

The handle is rosewood, presumably. It's so dark and dense that I can't be certain. The kasura needed to be set down more fully, because the dense wood doesn't compress as well as oak..... and they never seem to be set very well, anyways (the kasura/handle ring thingy).


No urasuki remaining on this guy, unfortunately. There is some rust pitting.

The back was fairly flat, but lately I've been trying to get my chisels VERY flat. I have this one most of the way done, but I need to check something else first.

So far, only artificial stones have been used, so I haven't gotten a look at the lamination line yet.

I've got a feeling about this chisel. I *think* that this chisel will have a very thin and delicate hagane, and as I'm working on this chisel, it reminds me of another chisel that I was working on a while back.



I bought a chisel quite a while ago, and initially it was one of those "What the hell was I thinking?!" kind of purchases.

As received, the chisel was.... Small. Also dry, dirty (The handle was so black from iron staining that I couldn't tell what type of wood it was made from. I had originally bought it thinking that the handle was ebony, haha!) and slightly corroded. But mostly it was small, and though I thought it a little bit, um.... un-manly, I tried it a few times and found it to actually be a fun tool to use. These little chisels fit right into my hand, and so small that you almost forget that you are holding them. The control is phenomenal! It's as easy to use as pointing your finger, and really feels as though it is an EXTENSION of your finger (if your finger was a super-sharp laser beam type of finger, haha!).

Anyway, I prepped this little chisel, and though I never finished giving it the full-on sharpening treatment, I did remember one impression in particular. The hagane seemed rather thin.



As I began cleaning up the little chisel, I figured out that it was a bit unusual and kind of nice.

I think that the style is called suminagashi (ink pattern), and it is similar to the more familiar mokume (wood grain), which looks like the even more familiar Damascus.


None of this was evident when I bought the tool, but only revealed itself after lots of scrubbing, de-rusting, chemical etching, and blackening.

I was surprised.


The ura side isn't too messed up, thankfully.

The ferule is hand forged, and a little rough, with lots of character.

The top ring is similar.

And here's that thin hagane that was previously only a hint.

Very thin for a chisel, the lamination line is clear and distinct. The upturned corners are very crisp and even. I was hoping for a ren-tetsu jigane, but you can't have 'em all, I suppose.

The blacksmith who forged this tool was very skilled, and it is these types of details that I want to incorporate in my own work. I've got a long way to go though.


OK, back to the other chisel. The point that I wanted to remind myself of, was that before I get too carried away, I need to polish the bevel a bit. That reveals the steel lamination line (at least if you use the right stones).

It IS thin, as expected. If I make the back of this chisel (obsessively, compulsively) completely flat, I run the risk of someday running out of the hard steel hagane. It's flat enough as it is, so I give it a rest.



Yeah, I know...... Lots of words, but not saying much, mostly just showing off some pretty tools.

I suppose that if there *had* to be a point to this post, it would be to check the lamination before zealously flattening the back of a Japanese chisel. Sometimes the nice tools use very thin laminations, and if you go too far.....

This is a great chisel, an Umehiro 48mm tataki-nomi, and it's a brute.

A small problem, though. The hagane is too thin at the corner on the right.

This corner doesn't hold an edge very well....Let me clarify. The corner itself is great, but that little spot where the soft iron intrudes? That little spot dents almost immediately. It's like having a permanent chip in the blade.

I am sure that if I ground the blade back about 4-5mm, I would be back to an area that had sufficient steel to hold an edge. I am loath to do that, and would rather put up with the perma-nick, rather than shorten the life of the chisel by 5 years.


Still, it has a nice backside.

The hollow was perfectly shaped, and the various users over the years haven't messed it up.

This is a high quality tool, and the blacksmith forged this blade with care. The little problem with the corner wouldn't be an issue if the previous users had done ura-dashi on this blade.

 I enjoy ura-dashi so much, that I do my chisels, too.

Segue....

Diamond everywhere! Testing some cheap diamond files for sharpening

More sharp!!....... Inexpensive , China made, diamond tools for sharpening the hardest Japanese tools. It's amazing how cheap ($) this stuff is getting.



I had bought a set of small detail bits suitable for a dremel type tool (1/8" shank). They worked well, and proved sufficiently durable, that I bought a larger set (1/4" shank).

Set of six, 1/4" shank, $11. 

I specifically got these for carving out profiles on some small kanna blades, used for cutting edge profiles. They seem to work just fine, the diamond grit is evenly distributed, and well adhered. If used with a light touch, these should give a respectable service life.



It’s pretty much impossible to determine *exactly* where any of these tools are made, so performance is unpredictable. At the other end of the performance spectrum are these diamond fingernail files. Diamond tools are everywhere!

4 For $1(top), and $0.99 each (bottom)

The upper package was found at the $Store (4 files for a dollar, I used one already.) The two at the bottom are $0.99 each at Walmart. Shockingly expensive, haha!

The $0.99 files are small, cheap ($), and cheap (quality). They work, to a limited degree, but lose their abrasive qualities rather quickly. #220 grit or so.

New on top, and after a few minutes of light work on steel (bottom).

They would probably work just fine on fingernails, but I'm using these files for harsher duty. Japanese plane blades, high carbon steel, HSS......whatever is too hard to sharpen with a standard file. 

The file on the right hand side is one of the cheapest-of-the-cheap $Store files. Larger, slightly more coarse (#180 grit), better looking and grit on all 4 sides. I was psyched to find these at the $Store, but they only had two packages remaining. I bought both!

$2 wasted! Service life can be measured in strokes, 1-2-3-done. I suspect that the file blanks are dipped in diamond fortified paint, as opposed to being electroplated. One file has a coating that stripped entirely off, after only a few minutes of VERY ineffective work. 

So, from the left, we have new $0.99, used (smooth feeling) $0.99, and $0.25 $Store file. 

Unfortunately, none of these are worth buying, even for a cheap guy like me.


For $11 (free delivery), these diamond files are 3" working length, come with 6 grits, and feel very durable. The electroplating, particularly on the scary rough #40 grit, is thick and holds up in use. These files work.

As the tool breaks in, more diamond surface is exposed, and the file becomes more effective. On short acquaintance, I am pleased.


I don't know much about Japanese saws, but I'm getting there. I bought a beautiful little $12, traditional 75mm yasuri feather file from eBay seller: Sakura-pink, to compare against a cheap ($11+free delivery) China-made diamond file.

Not my file-work, BTW! This saw is still fresh.

The sizes are comparable, but the "real" file has a slightly finer profile, and is MUCH faster in use. We shall see which is longer lasting.



About 8 years ago, I bought this knife sharpener at Walmart, for about $12. It has seen VERY hard use, and still works well. Some of this cheap China stuff is pretty damn good.

All diamond tools settle in after a period of time, sometimes minutes, sometimes months. This thing mellowed out after a few weeks, but then...... just won't stop working.

Coarse on one side, fine on the other. The fine is now around #600-800 grit.




If you have some serious metal to remove, but don't have access to a grinder, here is one way to do it by hand.

This kanna blade has had some serious ura-dashi done, and needs to start looking like a cutting tool again. The flat tip is nearly 1/8" thick..... That's a lot of steel to remove!

I tape a line, to act as a guide for establishing a new bevel. Most of the material to be removed is soft iron, so I can use a standard bastard cut file to hog out the bulk of it.

I love working this soft stuff. This only takes 2 minutes.

You can hear the difference, once you get to the hard steel lamination line. Stop, before you ruin your file.

Then use the diamond file, but ONLY on the hard steel portion. I have found that soft steel and iron can strip diamonds from the file (not these, but other diamond sharpening stones, so....), so ONLY use diamond on the hardest materials.

Finally, I finish the bevel using sandpaper stuck onto glass. This establishes a final, level surface over the entire bevel.

The 3M 3X line of sandpaper comes in funny colors, and uses a ceramic abrasive that fractures down nicely in use. It lasts WAY longer than the other common abrasives (al-ox, silicone-carbide, etc.) and only cost slightly more. Money well spent.

Although this was an extreme example, this blade only took about 15 minutes to get to the stage where the sharpening part starts. That's not bad, by my book.

I could've used JUST sandpaper (the good stuff)...... Maybe 2 sheets (so, $3 for sandpaper) and 30 minutes time. It *feels * like harder work, though.