This weekend in California is Kezurou-kai, an event to celebrate all things Japanese woodworking. The event culminates with a plane shaving contest where people compete to take the thinnest shaving of wood using Japanese hand planes. It’s a really fun event, with tons of generous people who are excited to share and talk about Japanese woodworking. Being here in Tokyo, I’m unable to join in the festivities but thought I’d participate in spirit by doing some sharpening.
It’s been a couple years now since I first posted about using hollow grinding and double bevel (micro-bevel if you prefer) sharpening methods on kanna, and I really have no complaints. I continue to use the same sharpening method for all my blades and have found hollow grinding, and especially the double bevel, have made my sharpening in general faster and more consistent. And that ultimately means I get to do more planing.
To that end I thought I’d share a short video showing the double bevel method on three blades using the same set of three synthetic stones. The stones are a Naniwa Hibiki 1000 grit stone, Kitayama 8000 grit, and Naniwa Kagayaki 12000 grit. It’s not shown in the video but I flattened each stone between sharpening sessions using a diamond plate.
The steel of the blades are each different; one white steel (Osahiro), one Swedish steel (Ishido), and one swallow steel (Tsunesaburo). The swallow steel is a heavily alloyed steel, which you can visibly see, followed by the Swedish steel with fewer alloys, and finally the white steel which is really quite “clean” in comparison.
To be honest the properties of different steel types has never really interested me. If a blade sharpens relatively easily and cuts well, that’s good enough for me. But lately looking at blades under the microscope after sharpening, and visually seeing how steels of different varieties turn out has really started to intrigue me. There’s a ton to talk about when it comes to different steel types but I’ll set that discussion aside for the time being.
My approach for each blade is:
- Sharpen the whole bevel on the rough stone (a quick round on the rough stone tends to reduce the size of the previous double bevel but not totally eliminate it)
- Double bevel on the 8000 grit stone, followed by a light pass on the ura (back) side of the blade
- Double bevel on the 12000 grit stone, followed by a light pass on the ura side.
A couple final notes- I lost the footage from sharpening the Ishido blade on the 8000 stone, but still included the results from that stone in a photo taken under the microscope. Also on the Osahiro and Tsunesaburo blades, I experimented with sharpening on the final 12000 stone using only pull strokes. This is something that I’ve been playing around with from time to time. I can’t say whether it’s a valid technique or not, but it definitely draws out the edge, creating an edge that’s extremely “grabby”. Finally, magnification of the images is around 400x.
Hope you enjoy, and feel free to comment below.
Hey Jon! Questions for ya. Since the 1000 often wasn’t touching the edge could you hypothetically just start at 8 for the same ending? And have you noticed any difference spending more time and taking lighter passes on the 12k than you did in the video? Assuming no, and that you analyzed things. Lastly, what do you use your swallow steel for? That steel seems hard to get as fine as the others on the finish stone.
Hey Brian,
“Since the 1000 often wasn’t touching the edge could you hypothetically just start at 8 for the same ending?” Yeah, and in fact that’s exactly what a friend of mine does. I prefer to hit the 1000 regularly just to keep knocking the micro bevel back and to prevent it from becoming too large. My buddy tends to re-sharpen a few times only on his finish stones, working just the micro-bevel a few times before finally spending some time reworking the main bevel.
“have you noticed any difference spending more time and taking lighter passes on the 12k than you did in the video?” I’ve played around with more passes, fewer passes, heavier and lighter pressure, etc. What I’ve found is that the micro bevel is so small that just a few strokes and modest pressure is usually enough to finish the edge. I like to check under a pocket microscope and when the edge becomes as straight and smooth as possible that’s usually where I stop, and it doesn’t take long to get to that point in my experience. Beyond that I’m not sure there’s any benefit to spending more time on the stone. That said every blade is different, and I’m sure there are some subtleties worthy of exploring.
As for the swallow steel blade, I really don’t use it much. And it has never been as fine of a blade as others, which is pretty clear from what you can see in the video. I mainly included it in the video for contrast.
Thanks. Then, this post to me is really about the use of a microscope to read what is happening and make choices on stone use and method in a logical way. I noticed my teachers spend more time on the finish stone than I did so I have been extending that. Full bevel work is different as you noted. But maybe I need to set up a more easy to use scope situation to encourage more frequent checking.
I think a microscope is a pretty awesome tool. It’s certainly not a necessity, but having one, even a cheap pocket microscope, really opens up a whole new world of information.
One of the take-aways for me using a double bevel method and seeing the results under the scope is just how quickly finish stones can cut when all of your effort is concentrated on the edge. One thing that I would like to do next is compare the results of double bevel sharpening vs standard sharpening under the scope. Working the full bevel definitely takes a lot more time since the area you are working is so much larger, but I’m also curious if the final result can give an even finer edge, since pressure on the stone is less concentrated. In other words, I imagine working the full bevel results in the bevel sort of skating over the surface of the stone engaging more with slurrly, etc. Whereas the double bevel method really cuts straight through any slurry, right to the stones surface. Just a thought but something I’ve been curious about.