Sharpening Kanna : an Evolving Method Part 4

Yamamoto Kanna – Extreme Macro

Over the course of the past year of so, I’ve been using a pocket microscope more and more frequently during sharpening. Even a cheap $20 scope can really show you an amazing amount of detail. It’s definitely not necessary to see the edge at high magnification and a lot of people never bother. But if you do use a scope it really reveals a lot of information. Especially when experimenting with different sharpening techniques and different stones.

One thing that I’ve really been wanting to do is to share the images that I’m seeing through the microscope. I’ve never able to get any decent quality images by using my phone’s camera through the scope. So I started to look around for alternatives. Then I stumbled upon the crazy niche world of folks who are attaching microscope lenses to dslr/mirrorless cameras. Most of these people are taking photos of insects or fungi, etc. But the overall setup seemed like it could work for taking pictures of kanna. After ordering more and more attachments for my camera than I ever imagined I would need, I ended up with a setup like this. This is a pretty slapped together setup, using tools/things I had available. But I’m planning to make little upgrades here and there to make the whole process smoother.

The main components are a Nikon 40 x microscope objective mounted on bellows attached to my camera. The 40x objective is capable of magnifying a 0.59 mm section of blade onto the full width of my camera sensor (23.6mm). Ultimately the actual magnification depends on the display width of the images on your screen. Right now on my screen, the image below is showing at about 180mm wide. 180/0.59= about 300x magnification. (The full size images are much larger). The image below is of a Yamamoto 鉄心斎 (tesshinsai) kanna after planing some cherry for a recent project.

Next up is the same blade after resharpening on a 400 grit Kensho stone:

At this magnification a frustrating amount of dust and debris start to show up. In the image above I wiped the blade with a rag after sharpening and a tiny fiber got stuck to the burr on the edge.

Next up I did a microbevel on an 8000 grit King stone:

The transition between the coarse stone and the micro-bevel is pretty cool. The edge still looks pretty jagged but even in this condition it can cut wood pretty well.

After the King stone I worked the micro-bevel a touch more on a 12000 grit Naniwa stone:

The edge got noticeably better, and the overall depth to the scratches on the edge look much shallower. It’s far from perfect, but for general work this kind of edge is totally usable.

For something completely different, I took the same blade after the 12000 grit stone, and stropped it on a piece of leather with a polishing compound:

I took about 15 strokes on the leather and you can see the results are pretty dramatic. The edge looks much softer and more rounded, and the transition between the micro-bevel and 400 grit scratches gets blended quite a bit.

I put all of these images together with a video of me sharpening this Yamamoto blade. Hoping to show how quick it is to sharpen a blade using a micro-bevel. One thing that I think becomes clear when you see the video along with some extreme macro photos, is how fast even a 8000 grit finish stone can cut. Particularly when doing a micro-bevel and focusing the pressure on the edge. Even when jumping from a course 400 grit stone up to 8000, you can see how quickly the 8000 stone is able to smooth out the course scratches.

https://www.youtube.com/watch?v=JO0RzDrIbrQ&ab_channel=BigSandWoodworking

In the video above I said that the images were approximately 400x magnification. Partly because the images appear larger than here in this post. But another way that someone recently explained it to me goes like this. A lot of people use a Peak 100x magnification scope, with a 10x objective to look at the edges of kanna. If you put a 40x objective on that scope the images would look similar to what I have pictured here, and the magnification would become 400x. So the images I’ve taken are approximately how the blade would look if viewed through a 400x microscope. One thing that I’m planning to do as soon as possible is to start including a scale in my images. Hopefully that will make the level of magnification much more clear.

A huge inspiration for all of this has been the Science of Sharp blog. For anyone who finds this topic interesting I highly recommend you check out that blog. The author is taking photos of the edges of blades using an electron microscope and the images are mindblowing. They are far more detailed and scientifically presented than I’ve done here. I also appreciate the author’s decision to not draw too many conclusions from his images. Instead he often leaves it up to readers to interpret the results. I may adopt that attitude here as well. After all the more experience I have sharpening the more I realize how much I really don’t understand. I’ve learned a lot by reading that blog, I hope you all go check it out.

I hope to have more of these photo experiments up over time. If anyone has any particular ideas or something they’d like to see let me know.

Thanks for reading,

Jon